Google Analytics now supports automatic currency conversion. Currently, this requires a manual mapping in Tealium because it isn't included by default in the tag template, and there's no option for it in the mapping toolbox (this will be updated in a future release of the GA tag).
All you need to do to enable automatic currency conversion is to map _ccurrency (E-Commerce) to "currencyCode" and Google will convert the currency you have passed in (ISO currency code e.g. GBP, USD) to the default currency for that GA account. Please note that the exchange rate is controlled by Google and not by Tealium. Follow these steps if you wish to use this functionality: