Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$87.25	10.730%	$96.6119	$96.61	$96.60	$96.60
Purchase #2	$203.29	9.385%	$222.3688	$222.37	$222.35	$222.40
Purchase #3	$205.58	5.320%	$216.5169	$216.52	$216.50	$216.50
Purchase #4	$157.98	5.248%	$166.2708	$166.27	$166.25	$166.30
Purchase #5	$60.30	8.549%	$65.455	$65.46	$65.45	$65.50
Purchase #6	$94.85	7.730%	$102.1819	$102.18	$102.20	$102.20
Purchase #7	$243.25	9.725%	$266.9061	$266.91	$266.90	$266.90
7 purchase totals =	$1,052.50		$1,136.3114	$1,136.32	$1,136.25	$1,136.40