Anyway, you're best off using a credit card in all these places. If you're taking ship's tours, there's really no reason to change any money if you have a credit card. If you're going out on your own in Helsinki and Copenhagen you should change maybe $50 into each currency before you go, so you can get tram tickets, boat rides, coffee and the like. In Estonia, EVERYBODY takes credit cards, including the sidewalk cafes, so there's no need to have local currency even if you're fending for yourself.
Obviously, US dollars are not official currency in any of these places. You might find a cab driver who'll accept them, but stores prefer credit cards
When we traveled there last year, the merchants and street vendors did not accept U.S. dollars. There were a few exceptions in Tallinn. As noted above, the credit cards are probably your best option, and you may want to ask your companies about the % they charge on top of the wholesale conversion rate. It's usually 2-4%. We had our local bank get about $50 of each currency before we left the states, and that was usually enough for us so the we didn't have to hit the ATMs too often. It's a lot to keep up with but unfortunately, these countries are not on the Euro, so it's like the old days of travel to Europe about 5-6 years ago. In other words, credit cards are widely accepted but the various currencies and conversion rates make it hard to keep the money matters straight. I strongly advise against changing $$ on the ship because they do not give you the wholesale exchange rate, and there will be a $7 or so charge for each transaction. If you have $10 U.S. or so leftover, you might as well spend it in the shops near the ship because you'll lost it in the exchange. The banks are a little better because they give you a good conversion rate but they still charge a transaction fee.
Thanks everyone for your replies. What if I only want to get a soft drink while walking through these towns. I wouldn't want to use a credit card for that. I guess the next thing would be to use an ATM, right?
Excuse me, but I though these message boards were for getting and giving information. I asked a question, which does not mean I'm an "ugly American" as you so aptly infured. I am very willing to change my money into local currency when I travlel, which I have been doing for more that 15 years all over the world. My question was to those people who have had experiece in the countries I am about to visit, about how much money would me needed to change? Thank you for much for your comment, I really needed a shot in the arm this morning.