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	$151.34	6.713%	$161.4995	$161.50	$161.50	$161.50
Purchase #2	$157.34	13.387%	$178.4031	$178.40	$178.40	$178.40
Purchase #3	$71.60	7.511%	$76.9779	$76.98	$77.00	$77.00
Purchase #4	$58.35	5.122%	$61.3387	$61.34	$61.35	$61.30
Purchase #5	$226.55	8.265%	$245.2744	$245.27	$245.25	$245.30
Purchase #6	$115.91	13.624%	$131.7016	$131.70	$131.70	$131.70
Purchase #7	$80.43	12.150%	$90.2022	$90.20	$90.20	$90.20
7 purchase totals =	$861.52		$945.3974	$945.39	$945.40	$945.40