SAN FRANCISCO (Reuters) - Facebook Inc wants more credit for making online cash registers ring. Facebook will begin rolling out on Friday a new tool which will allow online retailers to track purchases by members of the social network who have viewed their ads. The tool is the latest of the new advertising features Facebook is offering to convince marketers that steering advertising dollars to the company will deliver a payoff. Facebook, with roughly 1 billion users, has faced a tough reception on Wall Street amid concerns about its slowing revenue growth. ...{br}{br}View the Entire Article{br}