It is possible to limit discount and rounding by percentage or by rate.

Rounding Limitation: Tickets > Calculation Types > Round template.
Max. Amount: Write an amount to limitate. For example 20 ( It can’t make rounding over 20)

Discount Limitation: Tickets > Calculation Types > Discount template.
Max. Amount: Write an amount to discount. For example 20 ( It can’t make discount over 20)