Sally's website return policy about items purchased on the ground in a Sally's store mentions nothing about whether product must be new and unopened to be returnable. However, they can only be returned up to 60 days after the purchase date. I'd think at 3/4 full you could reasonably expect them to take it back.
CG since 11/2011
2c /3a F /Mii, low porosity

Fall Products /Routine:
Clarifying: Herbal Essences Tealightfully Clean
Low Poo: Renpure Luxurious Argan Oil
CO: Suave Naturals Tropical Coconut or Daily Clarifying, V05 Strawberry or Kiwi Lime
RO /LI:
Tresemme Perfectly (un)Done, Cure Care, V05 Kiwi Lime Squeeze, V05 Strawberry, Renpure Brazilian Keratin (old formula),
Stylers: LALSG, AIF, HETT
PT: IAGirl's as needed