I am certainly not a tax expert, but two names I hear more frequently are Avalara and TaxJar. Avalara have "AvaTax" on the Magento 2 marketplace, but I think TaxJar is still "coming soon", but will have some free offers. There may be lots of other good tax extensions - check out http://marketplace.magento.com/. The reviews there are probably more accurate than any opinion I have here. (I focus on Magento 2 architecture, not so much specific extensions.)