Avalara is good, if it is set up correctly. If not, you will spend all your time trying to get it right, Their support is comparable to any big-box SaaS — that is to say, it is difficult to get a human with actual tax expertise on your problem. If it were me and this was an option, I would pick a commerce platform that has sales tax support and keep it all in one place. Stripe has an add-on for tax that would probably do the trick.