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	$64.63	12.191%	$72.509	$72.51	$72.50	$72.50
Purchase #2	$47.50	7.146%	$50.8944	$50.89	$50.90	$50.90
Purchase #3	$155.32	8.619%	$168.707	$168.71	$168.70	$168.70
Purchase #4	$95.95	8.602%	$104.2036	$104.20	$104.20	$104.20
Purchase #5	$48.62	12.648%	$54.7695	$54.77	$54.75	$54.80
Purchase #6	$206.78	5.710%	$218.5871	$218.59	$218.60	$218.60
Purchase #7	$56.93	6.299%	$60.516	$60.52	$60.50	$60.50
7 purchase totals =	$675.73		$730.1866	$730.19	$730.15	$730.20