As a swiss, you're used to find it the first prices in Europe, not you don't think about other economies.
There's a comment in here from someone whose country recently switched to euros, and many small items there cost under 10 cents. Rounding down would make them free, rounding up doubles their price...
The measure is reasonable if the local economy is suited - Belgium and the Netherlands have been rounding bills for a good while now, but it's not something that should be pushed from the European level.
Not that I said rounding bills - individual items are stille priced to the cent. When paying by card, you pay the exact total, but when paying cash it gets rounded to the nearest 5 cent.