Surely, you can! Just head to your settings panel by typing 'settings' -->Time Tracking--> General Time Settings and find the "Round to the nearest minute" option and set it to whatever you need. 

Once this is set, say to 15, any punch in or out time will be rounded to the nearest 15 min, so a punch in at 9:27 will become 9:30 and any punch out at 9:06 will become 9:00.