It probably depends on the employer. I knew one man who worked for a leading Australian baker. Each time he delivered to stores he kept a few loaves aside and then sold them to his own customer. He thought that if he was ever caught he'd lose his job, but instead he was charged with embezzlement. He didn't do any jail time but he did get a driminal record.
Stealing from your boss -- even if it's only food for lunch -- isn't such a great idea.