Fuel%20costs,%20natural%20disasters%20and%20a%20weak%20U.S.%20dollar%20have%20driven%20grocery%20costs%20up%20by%205.4%20percent%20from%20July%202010%20to%20July%202011,%20according%20to%20Richard%20Volpe,%20an%20economist%20with%20the%20U.S.%20Department%20of%20Agriculture.

