Adding a Member's Price Line

I want to add a Members Dollar Price line that calculates a default of an additional 10% Off in the price line. The Members Price will calculate a dollar price lesser than the Sale Price, (or Retail price if there's no sale).

So customer will see:
MEMBER'S PRICE: $81.00
Sale Price: $90.00
Retail Price: $100.00

Please view the price line of ROVE CONCEPTS. It is the model site that gives the best example of what I want. Visit https://www.roveconcepts.com/