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	$209.81	11.297%	$233.5122	$233.51	$233.50	$233.50
Purchase #2	$176.79	11.191%	$196.5746	$196.57	$196.55	$196.60
Purchase #3	$111.82	10.185%	$123.2089	$123.21	$123.20	$123.20
Purchase #4	$30.49	3.605%	$31.5892	$31.59	$31.60	$31.60
Purchase #5	$50.94	10.733%	$56.4074	$56.41	$56.40	$56.40
Purchase #6	$114.87	8.243%	$124.3387	$124.34	$124.35	$124.30
Purchase #7	$116.55	4.791%	$122.1339	$122.13	$122.15	$122.10
7 purchase totals =	$811.27		$887.7649	$887.76	$887.75	$887.70