The currency in a listing is set by the seller and cannot be changed.
To view the prices is Canadian dollars you need to log on eBay.ca (Canada)
If the seller listed in Canadian dollars, that is what you will see
If the seller listed in US$ (and most sellers list in US$) you will see the US$ price and the equivalent conversion in Cdn$. That conversion is approximate, will fluctuate and does not include the 2.5% conversion fee charged by PayPal at time of payment.