U.S. stocks ended at three-month lows Tuesday, having slid during the final hour of trading, as investors continued to worry about Greece. The Dow Jones industrial average fell 63.35, or 0.50 percent, to 12,632.00. The broader Standard & Poor's 500 index lost 7.69, or 0.57 percent, to 1,330.66. The technology-heavy Nasdaq composite index dropped 8.82, or 0.30 percent, to 2,893.76.
