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	$179.40	6.295%	$190.6932	$190.69	$190.70	$190.70
Purchase #2	$76.93	12.777%	$86.7593	$86.76	$86.75	$86.80
Purchase #3	$202.30	9.783%	$222.091	$222.09	$222.10	$222.10
Purchase #4	$127.85	4.563%	$133.6838	$133.68	$133.70	$133.70
Purchase #5	$126.70	8.471%	$137.4328	$137.43	$137.45	$137.40
Purchase #6	$146.91	13.567%	$166.8413	$166.84	$166.85	$166.80
Purchase #7	$91.30	10.434%	$100.8262	$100.83	$100.85	$100.80
7 purchase totals =	$951.39		$1,038.3276	$1,038.32	$1,038.40	$1,038.30