This is a remix of 2ROBOTGUY's penny fidget spinner. The only change I made is that I added a 0.5mm top layer to each of the penny slots so that the pennies can be fully encased inside the spinner.
Instructions: I sliced the spinner using Cura 2.5 and then used GCode Simulator to visualize the layers from the gcode. Then I opened the gcode and added an M600 command (pause) just before the layer where the hole for the pennies is closed.
When printing, the printer should pause once the penny slots are done. Add 4 pennies to each slot (which should be even height with the top of the spinner at this point) and resume the printer. It should perfectly seal in the 4 pennies.
I use these bearings from Amazon.
Remixed with Tinkercad: https://tinkercad.com/things/dwgSh8iOmyE
Print at 99.7% scale for a tighter fit on the bearing.