While viewing products online, the website attempts to detect and reflect the currency based on the customer's current location whenever possible.  For example, if you're viewing a Canadian website from a United States address, the website will attempt to show all prices in USD; the current currency will appear near the top of the website, which you also have the option of changing to your preferred currency using the corresponding drop-down menu:
Once customers proceed to checkout, all prices and ultimately their receipt are automatically displayed in our local currency (CAD for a Canadian website; USD for a US website), but you'll automatically be charged in the currency associated with the credit card you use to make the purchase.