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	$158.50	9.126%	$172.9647	$172.96	$172.95	$173.00
Purchase #2	$224.88	13.447%	$255.1196	$255.12	$255.10	$255.10
Purchase #3	$47.64	10.166%	$52.4831	$52.48	$52.50	$52.50
Purchase #4	$133.36	13.776%	$151.7317	$151.73	$151.75	$151.70
Purchase #5	$153.27	12.506%	$172.4379	$172.44	$172.45	$172.40
Purchase #6	$177.38	8.843%	$193.0657	$193.07	$193.05	$193.10
Purchase #7	$92.49	7.410%	$99.3435	$99.34	$99.35	$99.30
7 purchase totals =	$987.52		$1,097.1462	$1,097.14	$1,097.15	$1,097.10