Optional tax

I need a module that allows my clients to choose whether to apply the tax to their invoice VAT (VAT is a Mexican tax). This tax has a value of 16% of the total invoice value. This tax will be a checkbox with a text instruction at side. Ex: A customer has an order of $500 assuming that the customer selects the checkbox the tax must be add 16% to the $ 500 for a total of $580

do you understand me?

I need this as a module. I will not sell it