I've been tinkering with building electronics and have needed to fabricate a few parts. A few days ago I found OpenSCAD and as a programmer I love the idea of doing solid object modeling using purely source code to define 3D shapes. OpenSCAD is fairly limited by itself, but if it doesn't do something you can always program it to do what you want. Here is a small OpenSCAD module to render rounded boxes.

module cubed(size = [10, 10, 10], radius = 0, center = true/false) 
{
    if (radius < 1)
    {
        cube(size, center);
    }
    else
    {
        move = center ? [0, 0, 0] : [size.x / 2, size.y / 2, size.z / 2];
        translate(move)
        {
            union()
            {
                cube([size.x - radius * 2, size.y - radius * 2, size.z], center = true);
                cube([size.x - radius * 2, size.y, size.z - radius * 2], center = true);
                cube([size.x, size.y - radius * 2, size.z - radius * 2], center = true);

                translate([size.x / -2 + radius, size.y / -2 + radius, 
                    size.z / -2 + radius])
                    sphere(radius);
                translate([size.x / 2 - radius, size.y / -2 + radius, 
                    size.z / -2 + radius])
                    sphere(radius);
                translate([size.x / -2 + radius, size.y / 2 - radius, 
                    size.z / -2 + radius])
                    sphere(radius);
                translate([size.x / 2 - radius, size.y / 2 - radius, 
                    size.z / -2 + radius])
                    sphere(radius);

                translate([size.x / -2 + radius, size.y / -2 + radius, 
                    size.z / 2 - radius])
                    sphere(radius);
                translate([size.x / 2 - radius, size.y / -2 + radius, 
                    size.z / 2 - radius])
                    sphere(radius);
                translate([size.x / -2 + radius, size.y / 2 - radius, 
                    size.z / 2 - radius])
                    sphere(radius);
                translate([size.x / 2 - radius, size.y / 2 - radius, 
                    size.z / 2 - radius])
                    sphere(radius);
                
                translate([size.x / -2 + radius, size.y / -2 + radius, 0])
                    cylinder(h = size.z - radius * 2, r = radius, center = true);
                translate([size.x / 2 - radius, size.y / -2 + radius, 0])
                    cylinder(h = size.z - radius * 2, r = radius, center = true);
                translate([size.x / 2 - radius, size.y / 2 - radius, 0])
                    cylinder(h = size.z - radius * 2, r = radius, center = true);
                translate([size.x / -2 + radius, size.y / 2 - radius, 0])
                    cylinder(h = size.z - radius * 2, r = radius, center = true);

                rotate([0, 90, 0])
                {
                    translate([size.z / 2 - radius, size.y / -2 + radius, 0])
                        cylinder(h = size.x - radius * 2, r = radius, center = true);
                    translate([size.z / 2 - radius, size.y / 2 - radius, 0])
                        cylinder(h = size.x - radius * 2, r = radius, center = true);
                    translate([size.z / -2 + radius, size.y / -2 + radius, 0])
                        cylinder(h = size.x - radius * 2, r = radius, center = true);
                    translate([size.z / -2 + radius, size.y / 2 - radius, 0])
                        cylinder(h = size.x - radius * 2, r = radius, center = true);
                }   
                
                rotate([90, 0, 0])
                {
                    translate([size.x / 2 - radius, size.z / -2 + radius, 0])
                        cylinder(h = size.y - radius * 2, r = radius, center = true);
                    translate([size.x / 2 - radius, size.z / 2 - radius, 0])
                        cylinder(h = size.y - radius * 2, r = radius, center = true);
                    translate([size.x / -2 + radius, size.z / -2 + radius, 0])
                        cylinder(h = size.y - radius * 2, r = radius, center = true);
                    translate([size.x / -2 + radius, size.z / 2 - radius, 0])
                        cylinder(h = size.y - radius * 2, r = radius, center = true);
                }
            }
        }
    }
}