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

Autumn Products /Routine:
Clarifying: ACV rinses, Suave Professional Men Deep Clean Peppermint
Low Poo: Renpure Luxurious Argan Oil
Co-washes: VO5 Kiwi Lime Squeeze or Strawberries & Cream
RO: VO5 KLS or S&C, Cure Care
LI (if needed): VO5 S&C, VO5 KLS, Cure Care
Stylers: FSG, L'Oreal Studio Clean gel, Tresemme Flawless Curls Bouncy Curls gel
PT: IAGirl's as needed