Most Canadian sellers list in US dollars because with ten times our population, the greatest part of our customer base is there.
In addition, all the world understands the US dollar and Americans understand nothing else.
If you are using eBaydotCA prices are given in both US dollars as the seller listed them and in Canadian dollars (marked as C$) right underneath. Note that the loonie price will fluctuate with foreign exchange but it is a handy guide.
If by chance you run across a US seller whose listings note:
Customs services and international tracking provided
That seller is using the Global Shipping Program. You will hate this.