Due to the limitations of the Shopify platform, we can only show an extra tax included price below the regular price on the product page.
If you would like us to show the changed prices on the checkout page, you should know that any changes on the checkout page are only possible on the Shopify Plus, and even then, there is very limited control over what can be done. If you are on Shopify Plus, you can reach out to us via chat or email at [email protected], and we’ll check what we can do for you.
The taxes part at checkout can only be controlled through the Admin account for your store, to which you can log in by going here. From there, you just need to go to Settings, in the bottom left corner of the screen, and then to Taxes.