I was really glad I had a €2 and a €0.20 coin at a tollbooth near Lyon recently when it rejected my credit card for the €2.20 toll.

Why would you not bring all your change? I have a little rubber coin purse that I load up with any destination-country coins and switch with my American coin purse en route. Any excess goes in a baggie for restocking — though I kept forgetting that last step on my recent trip and ended up bringing home way too much small change.