By CHRISTOPHER RUGABER and ANNE D’INNOCENZIO, Associated Press Business Writers WASHINGTON (AP) — Americans stepped up their spending at retailers last month in the latest sign that healthy consumer spending is driving the economy’s steady growth. Retail sales rose 0.4% from September to October, the Commerce Department said Friday, a solid increase though less than the previous month’s robust 0.8% gain. A 1.6% jump in sales at auto dealers drove much of the gain.