You have to remember who you are talking to. The clerks are probably either part time workers or university students working for the summer or whatever. They may be told the terminal will indicate two currencies if a foreign card is tendered. Press the button for cardholder currency. If they ask, tell them it's just an approximation for your benefit or whichever of the great lies the merchant has decided to use. Yes see you are being charged in euro but we list your currency as a service to you. They don't have a clue. You call over the manager and the manager may be somebody with slightly more experience. Or maybe he or she knows what's going on.

Of course, I have had managers tell me nobody ever complains and to keep the queue moving they don't bother to ask. And then the hassle begins about whether they can void a transaction. Meanwhile the queue behind you is getting longer. Of course, this assumes it is going on in an English speaking environment. What if it's not?

It may not be as simple as you would like to think it is.