U.S. stocks opened slightly higher on Tuesday as crude prices bounced back above $30 a barrel. ‘I think the norm now is for price swings in oil of about 5-6 percent and I think that’s probably the shape of things to come,’ said Michael Hewson, chief market strategist at CMC Markets, based in London. Though investors were still on edge following the 6.4 percent decline in China’s benchmark Shanghai Composite Index. Meanwhile, 3M (MMM) reported earnings of $1.80 a share in its fourth quarter, beating estimates of $1.63. Revenue barely eclipsed expectations. Plus, Procter and Gamble (PG) was hit by the strong dollar, which led to an 8.5 percent decline in quarterly revenue. Sales fell short of Wall Street's forecasts, though cost savings pushed the quarter’s profits up by 35 percent. TheStreet’s Scott Gamm reports from Wall Street.