Membership Discounts in Version 15

Hello, 

We are having an issue with membership discounts. We offer a 20% discount for memberships at certain times of year and use a promo code for that. Is there a way to do that while still having a fixed amount for start and end amount in your membership price. Due to our pricing tiers we cannot use a price range because it will overlap. 

Individual: $100 - 20% off is $80

Dual: $140 - 20% off is $112

Family: $200 - 20% off is $160

Family +CG: $220 - 20% off is $176 

Since $176 could fall into either a Family or a Family + CG membership when the contribution comes through Tessitura assigns these as Family memberships; which is not necessarily correct. We still offer full price memberships during this time. You must use the promo code to receive the 20% discount.

For example: we don't want someone purchasing a Family + CG membership with the 20% off to be assigned a Family membership and we also don't want someone purchasing a Family membership at full price $200 to be assigned a Family+CG membership. 

Is there somewhere else in Tessitura that we can indicate the lower discounted prices, similar to how we would for discounted admission tickets? So that the chart for membership levels doesn't need to change?