Where are you getting 5% cash back? Highest I've seen is Chase Sapphire with their points which are worth 2-3%. Highest straight cash back I've seen is Citi DoubleCash at 2%.
I have the old American Express Blue Cash card which has some crazy 5% cashback on gas and groceries once you hit a minimum spend during the year. That thing paid out like a slot machine when gas prices were hovering around $3.50 a gallon and I was doing a 100 mile commute daily.