I guess not? (Also I'm surprised Apple didn't include a "tip" field to guilt trip consumers into paying more)

No it’s not included.

There is no Federal sales tax in the US. As it is a lot of US states don’t tax software. I have seen companies handle this in a couple ways. Some have actually moved to collecting tax for the jurisdictions where they need to pay it, others just pay the taxes out of their revenue.

App Store doesn't show the state sales tax, but the tax is added to your receipt from Apple, just like for music, TV, and movie purchases. It's all the same system. And if you've made multiple purchases simultaneously (Apple likes to batch transactions), then the total sales tax is added at the end rather than individually to the items.

While it's feasible now, part of the reason it's historically not shown is that tax can vary by city borders, or even intersections of city/county borders where a city spans two counties. Zip codes aren't even enough granularity to get the right rate.