Hey, I honestly like the denomination $2.50. If you can have a quarter out of a dollar, why not a quarter off from a 10 dollar bill? Wait that's odd... now why isn't there a 25 dollar bill
Russia used to have some silly denominations like 1/8, 1/4, 2,3,4, 24, 30, 48, 75, 96 kopeks, 1.5, 3, 6, 12, 15, 37.5 ruble denomination. Now that's quite an impossible set to complete...

Nevertheless, a very neat type set!!!