Check your local Dollar General Weekly Ad circular to see if this applies to you:
http://weeklyads.dolla
Choose page view, the gift cards were on page 5 of my ad.
Picture in my ad shows a Lowes card where you can choose load values between $25 – $500. Obviously YMMV on what physical cards each store carries.
Remember Dollar General does not allow you to apply store coupons (eg $5 off $25 or receipt survey coupon on gift cards). Also most Dollar Generals only allow you to purchase gift cards with CASH.