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	$199.89	12.627%	$225.1301	$225.13	$225.15	$225.10
Purchase #2	$54.74	9.519%	$59.9507	$59.95	$59.95	$60.00
Purchase #3	$33.32	5.143%	$35.0336	$35.03	$35.05	$35.00
Purchase #4	$170.35	12.373%	$191.4274	$191.43	$191.45	$191.40
Purchase #5	$48.31	12.599%	$54.3966	$54.40	$54.40	$54.40
Purchase #6	$185.70	8.149%	$200.8327	$200.83	$200.85	$200.80
Purchase #7	$118.66	10.713%	$131.372	$131.37	$131.35	$131.40
7 purchase totals =	$810.97		$898.1431	$898.14	$898.20	$898.10