You add tax on your course selling prices in Academy LMS. You can add tax from the "System settings" as a percentage. If you add the tax to the course price, your students have to purchase that course with the tax price.

Figure 1. Academy LMS Adding Course Selling Tax

Figure 2. Academy LMS Course Checkout Page

Figure 3. Academy LMS Course Purchasing Page

For example, 

Your course price is $55 and you have added 2% as tax. 

$55x2%= $1.1 [Your course tax is $1.1. Your student has to provide this amount extra as tax with course price]

So the course price is:

$55+$1.1=$56.1

So, the student has to pay $56.1 for purchasing a course.

NB: To disable this tax amount, you can provide the 0% tax in the "System settings" option.