Shopping in the District of Columbia became more expensive as of January 1 because of a new mandatory five-cent tax on grocery bags. Local officials imposed the first-in-the-nation tax as part of DC’s Skip the Bag, Save the River campaign to clean up the Anacostia River, which has been plagued by sewage spills and other pollution, including plastic bags. Businesses are required to charge customers five cents per bag unless they bring their own. Stores get to keep one cent, and the other four go toward the river campaign, which is expected to raise $3.6 million in 2010.