Canada has a $2 coin. When I'm up there, I find myself using it a lot; an important thing in denominations is not whether each is a set multiple of the previous

Canada has a $2 coin. When I'm up there, I find myself using it a lot; an important thing in denominations is not whether each is a set multiple of the previous one, but whether the various denominations easily combine to produce common totals. So, for example, with $1, $2 and $5 denominations it's easy to produce pretty much any amount up to $20; then $20 and $10 make it easy to produce anything up to $100. And for anything more than $100 it's likely you're using a card or a check anyway.