Add or remove sales tax by province. Federal GST is 5%; some provinces combine it into HST, others add a separate PST.
Canada's federal GST is 5% everywhere. Five provinces fold it into a single HST (Ontario 13%; Nova Scotia 14%; New Brunswick, Newfoundland & Labrador and PEI 15%). Others add a separate PST/RST/QST alongside GST — British Columbia is 5% + 7% = 12% — while Alberta and the territories charge GST only at 5%.
To add tax, multiply the pre-tax price by one plus the combined rate; to extract tax from a tax-inclusive total, divide by one plus the rate. In PST provinces both taxes apply to the same pre-tax amount, not on top of each other. Registered businesses claim back the GST/HST they pay on purchases (input tax credits), so the tax ultimately falls on the final consumer.