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	$151.52	13.546%	$172.0449	$172.04	$172.05	$172.00
Purchase #2	$122.59	4.809%	$128.4854	$128.49	$128.50	$128.50
Purchase #3	$48.78	10.491%	$53.8975	$53.90	$53.90	$53.90
Purchase #4	$42.62	4.432%	$44.5089	$44.51	$44.50	$44.50
Purchase #5	$194.71	7.826%	$209.948	$209.95	$209.95	$209.90
Purchase #6	$90.89	10.744%	$100.6552	$100.66	$100.65	$100.70
Purchase #7	$161.76	7.422%	$173.7658	$173.77	$173.75	$173.80
7 purchase totals =	$812.87		$883.3057	$883.32	$883.30	$883.30