Re: TaxJar for v4
X-Cart has told me that they will not be releasing ANY X-Cart 4.X modules in the future.
TaxCloud is NOT the way to go. What they don't tell you on their website is that in the 24 "member" states of SSUTA is that they collect sales tax in these states whether you have an economic nexus in that state (because they collect a % of your sales, they force you to collect).
X-Cart Classic 4.4.X