One could also make a single transaction out to a series of smaller coins with a doubling sequence, so, half in one, half of the half in the second, etc, to one's taste, and then one will be able to make a payment from it at exact precision, with a small set of coins. The optimal efficiency pattern is 2s, 3s and 5s for the smallest coin set for any given payment amount, this gives you the equivalent of base 60 to divide things up perfectly in quarters, sixths, tenths, wha;tever you need.