Dollar General is on a path to dominate in America. Here's how it keeps its prices so low. (DG)

AP Dollar General is bucking the retail trend and expanding rapidly in the United States. It plans to open 900 new stores by the end of the year. The retailer is capitalizing on a growing trend toward more cost-conscious shopping. It offers prices that are 20% to 40% lower than grocery and drug stores. Here's how it keeps its prices so low. Dollar General is taking over the United States. This no-frills, bargain-hunters' paradise is growing at a level that is largely "unthinkable" in retail, Cre...