This is an accepted solution.
Elias here with Shopify Support. Thank you for reaching out to Shopify!
That's a great question! You can change the text labels across your theme and checkout by using the language editor. This is commonly used to help with translating the theme to a different language. More specifically, you can find the taxes label in the 'Checkout & system' tab of the language editor.
Here's what to look for in the language editor:
Then look for the taxes label:
Let me know if this helps! If you run into any issues finding the field for the label, don’t hesitate to let me know in this thread!