I created multi-language ubercart site using localization module. It allows to select 4 different languages.

For some langages, prices are in national currency.
If user selects certain other language, prizes must be shown in EUR using fixed rate.
Any idea how to get this result ?
Which places I must change ?
Or can anybody recommend other free cart (Zend Cart, Mageno, OsCommerce etc.) which has this feature ?