eBay will charge the fees based on the currency you selected for your eBay monthly fees.
If you selected Cdn$, eBay will convert the US$ fees into Cdn$ and charge your PayPal account in Cdn$.
If you selected US$, eBay will not convert and charge your PayPal account in US$. If you have no money in your US$ balance at PayPal, the amount will be converted into Cdn$ by PayPal (including a 2.5% currency conversion fee)
I noticed you sold an item a little over a year ago in US$. Check your billing history. The answer today should be the same unless you changed your billing currency in the meantime.