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	$160.55	7.430%	$172.4789	$172.48	$172.50	$172.50
Purchase #2	$194.83	5.292%	$205.1404	$205.14	$205.15	$205.10
Purchase #3	$228.47	13.749%	$259.8823	$259.88	$259.90	$259.90
Purchase #4	$129.60	10.780%	$143.5709	$143.57	$143.55	$143.60
Purchase #5	$102.79	13.568%	$116.7365	$116.74	$116.75	$116.70
Purchase #6	$203.75	12.848%	$229.9278	$229.93	$229.95	$229.90
Purchase #7	$172.66	4.756%	$180.8717	$180.87	$180.85	$180.90
7 purchase totals =	$1,192.65		$1,308.6085	$1,308.61	$1,308.65	$1,308.60