looking for an extension that can do:
a custom field (2 checkboxes) in checkout page
when checked , it will apply the tax to the subtotal price , like this screenshot
![Image](https://i.imgur.com/136rufu.png)
when left-side is checked or unchecked , the right-side's $3.78 will be added or removed and total price is re-calculated
thanks in advance.
best regards,