$5 for late pickups is too little an amount to deter the offence from occurring. I give a one time only 5 minute grace period, and then it's $20 for every 1/2 hr for every instance after that, even if it's 1-2 minutes late. Make it a significant charge if you want to stop it from occurring, otherwise they'll assume they can come late and just hand you the $5 without worrying about being late.