In America, at least, you should denominate your earnings in USD, even if they are held in a foreign currency.
"If you receive all or part of your income or pay some or all of your expenses in foreign currency, you must translate the foreign currency into U.S. dollars."
"If you receive all or part of your income or pay some or all of your expenses in foreign currency, you must translate the foreign currency into U.S. dollars."
http://www.irs.gov/publications/p54/ch01.html#en_US_2012_pub...