You need to use a reseller type company like Fastspring. There's no alternative - you either do the tax yourself or you make it so that you don't have to.

It's an extra 5% or so, but well worth it to avoid all the work and hassle of learning about and then paying sales tax in every country and region.

If you ever move beyond the "beer money" phase, you should be able to afford the experience required to do all this correctly using Stripe.