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	$208.51	8.871%	$227.0069	$227.01	$227.00	$227.00
Purchase #2	$158.54	4.637%	$165.8915	$165.89	$165.90	$165.90
Purchase #3	$146.58	7.470%	$157.5295	$157.53	$157.55	$157.50
Purchase #4	$100.89	11.353%	$112.344	$112.34	$112.35	$112.30
Purchase #5	$151.30	10.414%	$167.0564	$167.06	$167.05	$167.10
Purchase #6	$55.59	5.704%	$58.7609	$58.76	$58.75	$58.80
Purchase #7	$44.38	9.256%	$48.4878	$48.49	$48.50	$48.50
7 purchase totals =	$865.79		$937.0770	$937.08	$937.10	$937.10