having names for smaller denominations is not confusing..
back in the Victorian days the UK had:
farthing £0.0025
penny £0.01
tupence £0.02
shilling £0.05
pound. £1.00
fiver £5.00
tenner £10.00
..and so on
But back in the Victorian days, there was 12 pence in one shilling, and 20 shillings in one pound. That means one penny was £0.00416... and not £0.01.
Also, tupence is just two pence, and fiver and tenner are just 5er and 10er. If we follow this logic, then the most suitable names would be millies and mickeys, since they come from the suffix (milli- and micro-).