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	$105.45	5.820%	$111.5872	$111.59	$111.60	$111.60
Purchase #2	$236.50	7.774%	$254.8855	$254.89	$254.90	$254.90
Purchase #3	$122.38	8.620%	$132.9292	$132.93	$132.95	$132.90
Purchase #4	$60.73	13.342%	$68.8326	$68.83	$68.85	$68.80
Purchase #5	$42.80	11.445%	$47.6985	$47.70	$47.70	$47.70
Purchase #6	$136.54	13.211%	$154.5783	$154.58	$154.60	$154.60
Purchase #7	$34.32	8.534%	$37.2489	$37.25	$37.25	$37.20
7 purchase totals =	$738.72		$807.7602	$807.77	$807.85	$807.70