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	$247.28	3.707%	$256.4467	$256.45	$256.45	$256.40
Purchase #2	$242.30	12.419%	$272.3912	$272.39	$272.40	$272.40
Purchase #3	$142.58	10.179%	$157.0932	$157.09	$157.10	$157.10
Purchase #4	$6.52	13.799%	$7.4197	$7.42	$7.40	$7.40
Purchase #5	$128.33	7.263%	$137.6506	$137.65	$137.65	$137.70
Purchase #6	$154.26	12.371%	$173.3435	$173.34	$173.35	$173.30
Purchase #7	$169.83	12.843%	$191.6413	$191.64	$191.65	$191.60
7 purchase totals =	$1,091.10		$1,195.9862	$1,195.98	$1,196.00	$1,195.90