If it is over $20 value you will be required to pay Ontario HST sales tax of 13%
If it was not manufactured in a NAFTA country you may be required to pay duty.
There will be a service charge of $5 to $25 or more for brokerage from the shipper.
All of these are in addition to the Shipping and Handling the seller uses to pay his shipper.
Canada Post often does not bother to charge you if the seller uses USPS/Canada Post shipping. But if the thingie is bulky, don't count on it.