If you want to add tax to your Shopify product prices, you can change the "Currency Format" under "Store Details: Store Currency" on the settings screen.
Example of setting to add "(tax included)" to the price when the product price includes tax
[How to set it] Open "Settings: Store Details" > "Store Currency: Change Currency Format" and add the (tax included) notation.
[Supplementary information] Main locations where "HTML containing currency symbols" and "HTML not containing currency symbols" are used
