The euro is the official currency since January 1, 2002. 1 and 2 cents coins haven’t been adopted.
Banks generally open on weekdays from 9.15 to 16.15, and are closed on Saturdays and Sundays.
All banks changes traveler's checks with any problem (but with a commission about 7 - 11 euros) and accepts to withdraw money with card. Almost all cash dispensers accept Visa and MasterCard. You can also change at post offices, 9 to 17. On Sunday, some change office opens in Helsinki.