The HST is the Harmonized Sales Tax. They combined the federal sales tax (GST) with the provicial one (PST). Basically what happened then was they got rid of a bunch of exemptions. Also when they broght in the GST back in 1990, they would add that tax on to things that were basically already tax like stamps and other government fees.
When it came to gas prices here, there is a federal and provincial excise tax on gas (some of the larger cities like Montreal and Vancouver have their own as well. I think Rob Ford got rid of Toronto's.) In ontario they work out to almost 25 cents a litre (or $1/gallon.) Let's say the gas company is charging $.60/litre for themselves and the gas station. That brings the price up to $.85/litre. When they brought the GST in (then 7%, now 5%), they would add it to the entire amount of $.85/litre, not just the $.60 that the gas company was charging. (Using 5%) That would bring the price of gas to $.893/litre. If they charged it on to what the gas company was making, it would be $.88/litre. Since they harmonized the taxes, add 8% to that. Now it costs $.961/litre. If they just charged it on to what the gas company charged, it would be $.928/litre.
We pay 3.3 cents per litre for tax on a tax. In a city with their own excise tax, that amount will be charged and extra 13% as well for HST. I think BC has that. Otherwise it is just 5% GST.
That's all fine and dandy, but it's the same for all oil. I heat my house with that. When they brought that in, it basically now cost me almost an extra $100 a tank.
They government gave some "relief money" to help with the transition, but they were very indiscriminate about who they gave it to. In my case, they gave it to my then common law wife because her tax return was filed right before mine. I had the car and paid the bills so I got no relief.