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	$174.40	9.125%	$190.314	$190.31	$190.30	$190.30
Purchase #2	$154.87	3.370%	$160.0891	$160.09	$160.10	$160.10
Purchase #3	$212.95	4.390%	$222.2985	$222.30	$222.30	$222.30
Purchase #4	$54.38	5.733%	$57.4976	$57.50	$57.50	$57.50
Purchase #5	$212.57	13.390%	$241.0331	$241.03	$241.05	$241.00
Purchase #6	$57.54	8.253%	$62.2888	$62.29	$62.30	$62.30
Purchase #7	$137.50	6.470%	$146.3963	$146.40	$146.40	$146.40
7 purchase totals =	$1,004.21		$1,079.9174	$1,079.92	$1,079.95	$1,079.90