We have a huge problem with taxes when the product is in checkout. It calculates something that is not right. All the tax settings are just fine, and we tried every method to clear the problem, but it still appears, so the final is to appeal to you because it may be a problem with the theme
Please check how it works with the default WordPress theme and Woocommerce Storefront theme just to check whether the issue is with our theme or not. Also, please check the site with our theme but only with the theme default plugins activate, and deactivate all the 3rd party plugins from the site.
If it works fine with the default WordPress theme then provide the admin panel login details of the website to check it myself and help you out accordingly.