This mod is excellent if your importing products from multiple countries. For example, you import products in different currencies and you want to enter the imported price in the product price field. The customer will still see their own currency price on the website using the existing currency converter. Basically you wont need to do any conversions yourself into your default currency.
You can enter any currency price for the product in the admin side, but the customer will only see the currency they select.
Product Price (any currency) ->converted to Default currency price -> converted to Customer selected currency
Choose currency to change it sitewide.