Damn, what a rip off.
That's on everything you want to buy or just electronics and computer stuff?
In general, in a Canadian province that uses HST, the tax applies to every product that is sold to a resident of that province, no matter where the retailer is physically located, and every service that is consumed within the province.
(Except, businesses that do less than $30000 in sales quarterly, are not required to become HST-registered businesses, and non-registered businesses do not have to collect HST from their customers. But if a business owner does not register, then they cannot claim input tax credits to refund the HST they paid on their own raw materials.)
However, certain categories of products may be eligible for a reduced rate, they may be rated at zero percent, or they may be be exempt from the HST entirely. Products that are eligible for a reduced or zero rating vary from province to province, and may include certain essential products such as food ingredients (but not necessarily prepared foods), home energy, children's clothing, etc. The "full" HST ranges from 12% to 15% depending on what province you live in.
In provinces that have not signed up for the HST, a different value-added tax, the GST, applies at 5%. Again, there are reductions in the tax rate for certain essential products. (Such provinces may levy a separate sales tax of their own in addition to the GST.)