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	$236.32	8.519%	$256.4521	$256.45	$256.45	$256.50
Purchase #2	$121.71	3.733%	$126.2534	$126.25	$126.25	$126.30
Purchase #3	$250.58	7.485%	$269.3359	$269.34	$269.35	$269.30
Purchase #4	$174.60	12.338%	$196.1421	$196.14	$196.15	$196.10
Purchase #5	$175.45	11.312%	$195.2969	$195.30	$195.30	$195.30
Purchase #6	$214.90	12.743%	$242.2847	$242.28	$242.30	$242.30
Purchase #7	$77.72	10.316%	$85.7376	$85.74	$85.75	$85.70
7 purchase totals =	$1,251.28		$1,371.5027	$1,371.50	$1,371.55	$1,371.50