The shipping price generated by all WebShopApps extensions does not include tax. Deciding tax on shipping is outside the extension, we just return a shipping price, tax is managed separately. This is in line with all Magento shipping modules and all shipping extensions, the tax is not handled within.
In Premium Rate and ProductMatrix there is support for using Tax Inclusive Prices. This is for rule filtering e.g. you can say cart subtotal excl tax > $100 or cart total incl tax > $100. It has nothing to do with the tax on the shipping itself.