Given penicillin 500mg for a tooth infection. Says take every 6 hrs for 7 days. Can I take one dose late daily? I sometimes sleep longer than 6 hours.

Yes. The easy answer is yes. If your 30 min late on a dose it's not a huge deal. Just try to stick to the 6hr time frame as close as you can. If you're getting the appropriate total dosage in each 12-hr period you should be fine.
Keep to regimen. You need to take the pills as prescribed because the blood level dose decreases over time until there is no more active antibiotics are available for the infection. There is a higher dose of 875mg that can be taken twice a day.