Perhaps everyone else in the world knows about these, but I've only just found out. Apparently you can buy accurate looking mini-coins. My brother just gave me some, and they are very nice for my 1/4 dolls, but would probably be perfect proportioned of 1/3 sized.
I just thought I'd share in case anyone wanted their dolls to have their own currency!
(Sorry for the blurriness, I'm working with a phone while my camera is out for repairs)