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	$145.33	4.434%	$151.7739	$151.77	$151.75	$151.80
Purchase #2	$132.78	10.731%	$147.0286	$147.03	$147.05	$147.00
Purchase #3	$69.27	3.795%	$71.8988	$71.90	$71.90	$71.90
Purchase #4	$69.52	10.768%	$77.0059	$77.01	$77.00	$77.00
Purchase #5	$217.81	12.328%	$244.6616	$244.66	$244.65	$244.70
Purchase #6	$64.86	11.604%	$72.3864	$72.39	$72.40	$72.40
Purchase #7	$124.82	10.138%	$137.4743	$137.47	$137.45	$137.50
7 purchase totals =	$824.39		$902.2295	$902.23	$902.20	$902.30