It's tricky. It gets hairy around NY-NJ due to all this stuff (peak vs. off-peak) and since I-95 doesn't connect well, it also depends where you cross into Pennsylvania/Delaware, and if you have EZPass, which sometimes gets a discount. If you use the New Jersey Turnpike all the way from the GW Bridge, to I-295, and cross into Delaware, and you're going southbound at peak times, it's going to be about $26.30 if I did my math right.
The I-295 Delaware River Bridge is $3 southbound only, but there's a northbound-only toll in Maryland north of Baltimore which is $5. So it's about $28.30 from Virginia to Canada. That should be about right.