Ask HN: How do you keep up with taxes for international sales?

I've just taken a look at taxation for software sales. I wonder how anyone can keep up with the legality of it all.

For example I was looking if I (in Austria) would have to pay taxes in the USA if I sold something using the Apple App Store and how things change if I sell software from my own website. Finding any information about this stuff seems impossible without paying someone. Something that isn't cheap for someone just starting out.

Are there any resources online I haven't stumbled upon yet or is paying someone to look through this maze the sole solution?