I booked hotels in Italy on Expedia and was charged by some hotels in Euros. The Expedia agent explained that in some cases you are buying from Expedia in your own currency and sometimes you are buying from the hotel in theirs. In general, if you pay in advance and your credit card is charged, it is in the currency of the Expedia agency you use (.com = US, .ca = Canada). If you pay on arrival, it will be to the hotel in theirs.