I have an international Magento install that has 3 different websites, US, Uk/International, and Mexico. The reason for having 3 different websites is because we have a different payment gateway for each. We currently can accept either USD, Pounds, or Euros. Right now, the US and Mexico website's base currency is USD, and the UK/International website's base currency is Euros. However, I need to be able to accept all three forms of currency in each website. For example, if someone is purchasing a product from the UK/International store, I need them to be able to pay in either USD, Pounds, or Euros. I can get the frontend of the site to display prices in multiple currencies and the conversions look right. However when I actually place an order it only charges my card in USD.
For example, I have a product in the UK/International store that is 2.42 Euros (incl. tax). When I try to purchase it and pay with my American credit card, it charges my card the numerical value of the item in USD, in this case the value of the product is 2.42 Euros, but my card only gets charged $2.42, when it should be getting charged something like $2.86 (give or take current exchange rate).
So my question is how would I go about setting up the desired functionality?