SCs Currency Converter v1.2.2
This add-on converts all US Dollar, British Pound Sterling and Euro prices found on any web page to a user set currency, and replaces the prices with the converted ones. All conversion happens automatically, so no user activity needed.
You can choose from 164 different currencies.
Please note, that this add-on gets the exchange rates from Google, so their Currency Conversion Disclaimer applies here as well.