www.envioscuba.ca / www.carlostercero.ca is situated in Toronto - Canada and for that reason your bill is shown in Canadian (CAD) dollars as per Canadian law.
You should not worry about the dollar exchange since your bank is one who performs the transaction (if you have more questions about please contact your bank). From your account, we will charge the equivalent of the listed price on the website in Canadian dollars. In no manner are we increasing the total purchase amount of your order.
The exchange rates we use for EUR or USD are from www.xe.com