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	$149.27	10.821%	$165.4225	$165.42	$165.40	$165.40
Purchase #2	$238.40	7.267%	$255.7245	$255.72	$255.70	$255.70
Purchase #3	$227.63	6.484%	$242.3895	$242.39	$242.40	$242.40
Purchase #4	$222.48	5.422%	$234.5429	$234.54	$234.55	$234.50
Purchase #5	$246.35	3.713%	$255.497	$255.50	$255.50	$255.50
Purchase #6	$229.49	8.827%	$249.7471	$249.75	$249.75	$249.70
Purchase #7	$151.47	3.104%	$156.1716	$156.17	$156.15	$156.20
7 purchase totals =	$1,465.09		$1,559.4951	$1,559.49	$1,559.45	$1,559.40