Whether sales tax applies to shipping varies by locality/tax jurisdiction. It can sometimes even depend on both where the product is coming from and where it is going to. It gets even worse than that.. in the USA it can depend on which states the retailer has employees in. Online retailers generally use third party services to calculate sales tax because it's so complicated, and there can even be discrepancies between how to services calculate sales tax for the same order.
At least that was my experience when I worked on a shopping cart system for an online retailer in 2015-2016. They had a completely different system for order fulfillment vs the online shopping cart, and their in-house fulfillment system calculated sales tax more accurately than the online service the shopping cart used, and almost always higher because it was accounting for county-level and regional tax jurisdictions that the online service was missing. The fulfillment system operated on some ancient IBM system that didn't really know how to talk to the internet, so the shopping cart using it for sales tax calc at checkout was a non-starter.
Anyway I assume Shopify is calculating LTTStore's sales tax based on their business and the customer's shipping or billing address, and helps them with the process of actually paying those taxes to all the different municipalities that collected it.
Sales tax is soooo much worse than time zones and daylight savings... it's hilarious.
