Interesting, I'd find that super annoying as a consumer that's used to seeing the full price (ex. delivery) upfront. Is this standard practice for online US stores?
All stores in the US do this, online or brick and mortar.
It is annoying but taxes in the US are based on locality, so they involve state and municipal sales taxes, so it would be impossible to list one price for every customer.
It's standard practice in the US, full stop.
There’s probably more than 10k potential sales tax rates in the US, so you get used to it.
It is not like accountant does not calculate and pay the tax for each tax jurisdiction anyway.