Ability for Tiered Pricing to account for less than full toppings

For pizza, it would be nice if the tiered pricing feature would account for 1/2 or even 1/4 toppings. For example, if a merchant wants to allow for 2 FREE toppings on a pizza before they start charging, it would be nice if the system would allow 4 half topping to be picked or any combination... 1 topping and 2 half toppings for example. At the moment, if a half topping is added, it counts it as 1 of the full free toppings. I hope that makes sense.