If you are claiming interest and dividends from foreign sources, you should enter these in the Foreign Slip section of TurboTax. From here you'll be able to enter an exchange rate and TurboTax will make the currency conversion for you.
You can access this slip in the Online version, or the Easystep view of the CD/Download version by:
Or you can access it from the sidebar of TurboTax by:
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