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	$60.42	11.189%	$67.1804	$67.18	$67.20	$67.20
Purchase #2	$48.72	10.267%	$53.7221	$53.72	$53.70	$53.70
Purchase #3	$184.62	8.306%	$199.9545	$199.95	$199.95	$200.00
Purchase #4	$204.75	4.547%	$214.06	$214.06	$214.05	$214.10
Purchase #5	$90.79	5.292%	$95.5946	$95.59	$95.60	$95.60
Purchase #6	$62.36	12.762%	$70.3184	$70.32	$70.30	$70.30
Purchase #7	$183.25	7.210%	$196.4623	$196.46	$196.45	$196.50
7 purchase totals =	$834.91		$897.2923	$897.28	$897.25	$897.40