I went to Alaska in 2015, traveling through BC, Yukon, Alberta, etc. and used my VISA card. Didn't check and was charged about $125 total for conversion fees.
First time is a mistake, second time a sign of stupidity...:)
Last summer, when up to Quebec, Newfoundland, Nova Scotia and PEI and used my NEW VISA card that didn't charge conversion fees. My daily charges were converted at the daily bank rates without any fees. Had about $100 Cdn for incidentals and saved the hassle of going to Canadian Banks to get money or use an ATM machine with their $$$ fees.
Also found that the Canadians don't like American Express or Discover.
Had a great time and already planning a return to PEI and NS this summer.