I tried to use my 100E bill to pay for gelato...boy, did I get yelled at. They would not accept it, even after they handed my daughter her cone, and she had licked it! I ran to several different stores in the area to see if anyone would break it. NO.
My daughter had to hand the ice cream back to them, and she walked out. I finally found a shop, bought some cheese, they broke the 100E bill and we went to a different gelato shop to get our fix.
Lesson learned. Small shops generally will not break the bills for you. Make sure you break them when you can in resturants, etc when the bill is over 10E.
The 100E bill was the only bill I had. I'd just visited an ATM and was surprised when I only got the one bill...I thought I'd get 5 20E bills!
This happened in Rome at the Blue Ice gelato shop on the Campo di'Fiori.