Here in Norway we been removing less useful (meaning coins of little practical value) coins for years: - The 1 øre and 2 øre coins disappeared in '74 - The 5 øre and 25 øre coins were withdrawn in '84 - The 10 øre coin ended being legal tender in '92 - The 50 øre coin was withdrawn May 1st 2012. So while I can still recall putting a 5øre coin in my piggy-bank, there is now no coins circulating that is worth less than 1 Norwegian krone... but you know what? The wast majority of Norwegians pay by card anyhow, and the prices has not changed with the smaller coins going away. If you pay by card, you pay the exact amount. If you pay cash, it is rounded up or down to the nearest coin-value.
For those curious; after the retirement of the 50 øre coin, a purchase of 9.49 kroner is rounded down to 9.00 while a purchase of 9.50 kroner is rounded up to 10.00 - unless you pay by card, in which case you pay the exact sum owed. Off course it helps that the VAT is already added to the price listed - what you see is what you pay, but there is no reason why it shouldn't work equally well in places this isn't done (something which always boggles me when I'm visiting the US btw).
The US penny today is worth much less than the half-penny was when it was removed from circulation... yet for some reason people oppose removing the penny.