I second this. If you sell worldwide, there isn't any reason for you to handle the taxes and payment methods on your own. Actually, there's a whole bunch of companies that would do that for a relatively small cut (about 5% give or take). From the top of my head: 2Checkout, Bluesnap, DigitalRiver, FastSpring. I don't know much about Paddle, but they spammed me quite aggressively using the email from a leaked LinkedIn dump, so I'm not sure how much I would trust them.