I know this is not possible at this point, but this is URGENTLY needed and is a big loss for many European businesses that are using Squarespace.
It is required in B2C business model to show ONLY the end price where the VAT is already included. So you have to select the option where tax is already part of the product price.
But then there is an issue, if you want to deliver to non European Union countries (Switzerland is a good example), you are not allowed to collect German VAT from the Swiss customers, since it is a totally different amount and also, because the customs are imposing their local Swiss taxes when the package crosses the Swiss border. So this puts the business in a very non flexible position, where you need to exclude this country from the delivery list completely, which is not only financial loss of the potential revenue, but is also discriminating for the potential customers in non-EU countries.
Dear Squarespace team, there must be a very simple and easy fix for you, how to make it more flexible, it could be an easy option, where you can actually deduct the VAT, so let's say in the "Tax" section, I can also exclude particular VAT % from specific countries, so it is the same system as you have now, but just "negative", meaning it will remove the unnecessary tax during the checkout automatically. Sort of working like "discount", but obviously is legally and from taxes perspective reflected accurately on the invoice.
You have a great product, but this kind of flaws are pretty frustrating for someone who is in Europe and wants to try all the available options there is order to find the right target group and the right way.