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	$111.89	13.214%	$126.6751	$126.68	$126.70	$126.70
Purchase #2	$54.98	10.131%	$60.55	$60.55	$60.55	$60.60
Purchase #3	$183.70	4.456%	$191.8857	$191.89	$191.90	$191.90
Purchase #4	$247.76	11.245%	$275.6206	$275.62	$275.60	$275.60
Purchase #5	$131.59	3.834%	$136.6352	$136.64	$136.65	$136.60
Purchase #6	$120.98	9.669%	$132.6776	$132.68	$132.70	$132.70
Purchase #7	$134.44	5.485%	$141.814	$141.81	$141.80	$141.80
7 purchase totals =	$985.34		$1,065.8582	$1,065.87	$1,065.90	$1,065.90