In ideal world, I would prefer coins to be powers of 2.
It requires 7 coins in [ 1 .. 64 ] range to reach 100, but the average of popcnt( 1 .. 99 ) is only 3.19 coins per transaction, way better than 4.1 coins.
Now account for the amount of mental overhead required for the average person to calculate change or coinage of a random amount in base two coins, as opposed to multiples of 5 or 10, and see if your 3.19 coins per transaction really saves you time.
It requires 7 coins in [ 1 .. 64 ] range to reach 100, but the average of popcnt( 1 .. 99 ) is only 3.19 coins per transaction, way better than 4.1 coins.