In New Brunswick there are no tolls, so it's a free pass.
If you go to PEI there is no toll island bound, you pay to leave the island. I don't think the Fixed Link bridge recognizes EZ pass but here is the website: https://www.straitpass.com/default.aspx
In Nova Scotia the only highway toll is on the Cobequid Pass, part of Highway 104, which is the Trans Canada Highway through Northern Nova Scotia and directly between you and Halifax. Here's what their website says:
"No, currently E-Z Pass transponders do not work on the maritime toll facilities. A different type of transponder is required and a separate account for each maritime toll facility."
There are two toll bridges in Halifax as well, No EZ Pass. Tolls are $1.00 per car, I never drive my motorhome across them as they lead directly into major traffic. If you are driving your rig explore ways around them.
Credit Cards are accepted everywhere so your need for cash will be limited. I advise that you buy the small amount of cash you need from your bank as retailers here are all over the map when it comes to that issue. You need cash for the Cobequid Pass. With your 5th wheel it will be $5.25 CDN each way.
I should mention that when in Nova Scotia the beer requested should be "Alexander Keith's" or Keith's. Moosehead is still acceptable there but the bar tender might squint at you with one eye, in order to really check you out, if you order anything "from away"
