[FredPret]

The US has too many tax permutations for this to be practicable. Companies would have to make prices a bit higher to accommodate unexpected sales tax increases in some or other jurisdiction.

There's a small industry that specializes in knowing what the sales tax for a particular transaction should be at the moment it goes through.

[stetrain]

Knowing the sales tax at a particular in-person store is more feasible, and that’s the only case where you have to deal with cash.

If I’m buying online with a digital transaction you can charge whatever cents are necessary.

[FredPret]

You then still have the issue of standardized advertising prices.

Right now, a company can say they sell gadget X for $999, which would not be possible if they had to work out item taxes.

The other possibility is that they now have to mark X up to take into account the most pessimistic possible tax rate and advertise the marked-up rate.

[SoftTalker]

Forcing the simplification of all those taxes doesn't seem like it has a downside, to me.

[FredPret]

That would centralize power to the larger taxing authority.

Right now, there's a huge number of elected people in the US who wield real local power through these taxes and other rules that they can make.

It's a headache but we live in the computer age and we can automate administrative things like tax calculation at checkout; we should be using systems to aid decentralization and democratization instead of the opposite.