Most sites we used were in Canadian dollars.
You should use a credit card to get the best exchange rate on date and time used.
We used cash machines to get Canadian money after crossing into our friends to the north. See if your bank has an affilliate in Canada
Fuel costs need to be converted from liters to US gallons and then price converted to US dollars to get a better comparison.
Our last trip through Canada found the converted prices were close to what we were paying in Washington state at the time.