Hi, I know this is an old thread but hopefully, you got the issue fixed. If not, you can fix it easily by going to your Shopify Admin page => “Settings => Taxes and Duties” scroll down to “Decide how tax is charged”
(1) I believe your selection might be “Include tax in prices.” (Uncheck that box)
(2) Check the option below (Charge tax on shipping rates.)
That will fix your issue. You’re welcome.