How do I calculate commissions for employees if the following were to occur:

If an employee has 0-100 dollars in sales, there is no commission.
If an employees has 100-200 dollars in sales, there is a 5% commission.
If an employee has 200-300 dollars in sales, there is a 10% commission.
If an employee has 300+ dollars in sales, there is a 15% commission.

Peter