Or just buy the Lyman weight check set:
It comes in a small little box that is a lot easier to store than baggies filled with empty cases and aluminum foil. Admittedly it is not virtually free but I think handier and more versatile as it allows for a better check of the full range of the scale.
My Dillon digital scale is about 15+ years old and works today the same as it did when new. I check it against the weight check set occasionally.
But for those on a budget your approach is much better than nothing.