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	$200.89	7.590%	$216.1376	$216.14	$216.15	$216.10
Purchase #2	$71.28	7.348%	$76.5177	$76.52	$76.50	$76.50
Purchase #3	$89.81	11.873%	$100.4731	$100.47	$100.45	$100.50
Purchase #4	$79.91	4.110%	$83.1943	$83.19	$83.20	$83.20
Purchase #5	$139.39	11.537%	$155.4714	$155.47	$155.45	$155.50
Purchase #6	$74.70	13.670%	$84.9115	$84.91	$84.90	$84.90
Purchase #7	$222.93	12.248%	$250.2345	$250.23	$250.25	$250.20
7 purchase totals =	$878.91		$966.9401	$966.93	$966.90	$966.90