With a single Federal Goods and Services Tax (GST) as in Australia, you know it is 10%. All prices include the GST and are the price you will pay. There are no other sales taxes. Everyone knows what the government's cut is. Everyone knows how much they are actually paying. I can't see why anyone would want a more complicated system.

Clarification: Many "essential" goods like simple foods are GST exempt. They will be marked as such on the receipt. Again, the price on the shelf or box is what you will actually pay. There are no hidden surprises.

Though there are still some special cases where they sneak in extra taxes - stamp duty on houses and import duties on cars for example.

Is it 10% in all states?

In Canada, the provincial sales tax differs in each province. The federal rate is 5%. Alberta has no sales tax, whereas Ontario charges 8% (post-harmonization it's a HST of 13%).

In the US, the sales tax differs not only by state, but by county and city.

The tax situation in Chicago is particularly bizarre.

The sales tax in Cook County, where the city of Chicago located, is 10.25%. The sales tax one county over (say Dupage County, 15-20 miles outside the city and still part of the greater Chicago metropolitan area) is 8%.

Restaurants in the City of Chicago (but not other parts of Cook County) charge 10.75% because there's a city-specific restaurant tax.

The different tax rates create strange arbitrage opportunities. If I buy an iPhone from an Apple Store a few miles outside Chicago, I get an automatic 2.25% discount.

I wonder why does harmonization always infer a higher tax than the previous one. If we'd had harmonized VAT in Europe I guess it would be like over 20% and those with 19% or lower would end up paying more.

The harmonization in Ontario is more like combining the 5% federal rate and the 8% provincial rate into a single combined rate of 13%, so there’s no change in this case.

The 10% tax is at the federal layer in Australia and is the same across all states and territories.

FWIW, Canadian taxes are similarly quite uniform within a province.

Canadians also have a Federal GST, and provinces add their own tax, which gets added together into one Harmonized Services Tax (HST) in all provinces but Quebec and British Columbia, which have their own rules (QC collects an additional Provincial Sales Tax (PST))

Of course, there are fun additional taxes as well like the Environmental Handling Fee (EHF) on electronics.

In the US, there are different state, county, and local taxes depending on your location. There is no way to memorize a single number and have it be correct everywhere.

Not sure why this got downvoted. Absolutely you should know what you are paying so you can make informed electoral decisions.

You can't assume "everybody" knows.

I wish they made it in LCBO reciepts, so we could see that sweet almost 100% tax on alcohol.