Hi Alex,
Currency Conversion in Adobe Analytics is an excellent feature that allows you to send, collect, and display currency all in different ways. To preface this answer, read this article in its entirety:
http://microsite.omniture.com/t2/help/en_US/home/index.html#kb-using-currency-conversion
Once you have, the easiest/most accurate way to obtain this data you're looking for is to configure each report suite to store data in USD. You can send data to each report suite in whatever currency you'd like, and it will automatically convert it to USD upon collection. From there, you can send API requests to the report suite and no currency conversion is needed whatsoever.