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	$105.38	6.208%	$111.922	$111.92	$111.90	$111.90
Purchase #2	$116.61	6.427%	$124.1045	$124.10	$124.10	$124.10
Purchase #3	$50.98	5.121%	$53.5907	$53.59	$53.60	$53.60
Purchase #4	$173.74	5.658%	$183.5702	$183.57	$183.55	$183.60
Purchase #5	$199.79	11.538%	$222.8418	$222.84	$222.85	$222.80
Purchase #6	$196.58	13.384%	$222.8903	$222.89	$222.90	$222.90
Purchase #7	$158.42	11.863%	$177.2134	$177.21	$177.20	$177.20
7 purchase totals =	$1,001.50		$1,096.1329	$1,096.12	$1,096.10	$1,096.10