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	$162.35	6.162%	$172.354	$172.35	$172.35	$172.40
Purchase #2	$105.70	5.691%	$111.7154	$111.72	$111.70	$111.70
Purchase #3	$172.62	10.418%	$190.6036	$190.60	$190.60	$190.60
Purchase #4	$51.52	11.294%	$57.3387	$57.34	$57.35	$57.30
Purchase #5	$22.30	11.751%	$24.9205	$24.92	$24.90	$24.90
Purchase #6	$40.48	9.423%	$44.2944	$44.29	$44.30	$44.30
Purchase #7	$191.78	11.847%	$214.5002	$214.50	$214.50	$214.50
7 purchase totals =	$746.75		$815.7268	$815.72	$815.70	$815.70