HOUSTON – Do you have unused gift cards or some store credits that you haven’t used? According to the survey, Americans have more than $20 billion in unused cards or rewards. “Gift cards and store credits are real money, so treat them as such,” said Ted Rossman, an industry analyst at Bankrate. Millennials are the guiltiest of having unused gift cards. “You can sell unwanted gift cards at sites such as Cardpool.com, CardCash.com and GiftCardSpread.com,” Rossman said.