France did this yonks ago....
In pre Euro days I recall there being no 1 or 2 centime coins. I did see an item in a supermarket priced at some francs and 97 centimes, which I bought, hoping to see some very tiny coins, but no - rounding took place.
I only hope that when I buy a penny sweet with a five pence piece I get five pence change. Now that'd be fine rounding ;-)