This is one of those logic puzzles, about how many bills you can end up with in your wallet (you dump the coins in a dish at home each night, of course).
Because if you start with $1000 in fifties, say, the first time you buy something (not using hundreds because many places don't like them), you'll get smaller bills back in change, but the next thing you buy you can probably use some of the smaller bills, so you'll never end up with 50 ones.
I like to keep a balance of $5-10 in ones, and the rest in twenties, with $5/10 sometimes appearing.
Because if you start with $1000 in fifties, say, the first time you buy something (not using hundreds because many places don't like them), you'll get smaller bills back in change, but the next thing you buy you can probably use some of the smaller bills, so you'll never end up with 50 ones.
I like to keep a balance of $5-10 in ones, and the rest in twenties, with $5/10 sometimes appearing.