Updated from 4:09 p.m.Stocks hugged the flatline Wednesday as an early push to the upside gave way to profit-taking and volatile trading in the afternoon. The Dow Jones Industrial Average closed with a gain of 12 points, or 0.1%, to 8793, while the S&P 500 rose 2 points, or 0.2%, to 953. It was the fifth straight session of gains for both. The Nasdaq rose 7 points, or 0.4%, to 1563. "The market just got tired," said John Davidson, president and chief executive of PartnerRe Asset Management. "There's not yet enough proof of substantial economic growth, so it is difficult to expect the markets would go up straight from here." Meanwhile, President Bush signed a $350 billion bill that will give tax breaks to individuals, companies and investors. The tax package approved by Congress was less than half the size Bush had initially requested. Despite directionless prices, investors were fairly active. On the NYSE, 1.5 billion shares were traded, with advancers outpacing decliners by a ratio of 8 to 7. More than 2 billion shares traded hands on the Nasdaq, with winners leading losers by a margin of almost 8 to 7. Retail shares were led higher by Costco ( COST) after the company said fiscal third-quarter earnings rose 18%. Costco shares gained $1.43, or 4%, to $37.35. Elsewhere, SBC Communications ( SBC) could soon purchase some wireless spectrum from NextWave Telecom ( NXLC) through Cingular Wireless, a mobile-phone unit it owns along with BellSouth. The deal could be valued at $1.5 billion, according to media reports. Shares lost 13 cents, or 0.5%, to $25.32. RealNetworks ( RNWK) said it will begin selling songs for 79 cents each over the Internet, undercutting Apple Computer's ( AAPL) 99-cent offer. Shares gained 95 cents, or almost 12%, to $9.15. Rambus ( RMBS), a designer of computer memory chips, was up $2.26 to $18.70. A federal court dismissed a class-action suit that accused the company of improper conduct in trying to get its proprietary technology adopted as the industry standard. Shares climbed $1.11, or almost 7%, to $17.55.