I had to glue the US penny, but you might be able to tweak the hole in OpenSCAD further. It is functional and attaches perfectly to my pegboard by my workbench, which is exactly what I needed. Cheers!

Slicer Specs

PLA
25% Sparse infill density
3 Wall loops
Rectilinear infill
Tree(auto) Support w/ 6mm First layer expansion
6mm Mouse ear brim