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	$162.91	3.179%	$168.0889	$168.09	$168.10	$168.10
Purchase #2	$43.58	4.863%	$45.6993	$45.70	$45.70	$45.70
Purchase #3	$191.89	3.494%	$198.5946	$198.59	$198.60	$198.60
Purchase #4	$95.47	5.288%	$100.5185	$100.52	$100.50	$100.50
Purchase #5	$143.43	8.175%	$155.1554	$155.16	$155.15	$155.20
Purchase #6	$224.81	5.230%	$236.5676	$236.57	$236.55	$236.60
Purchase #7	$67.67	11.395%	$75.381	$75.38	$75.40	$75.40
7 purchase totals =	$929.76		$980.0053	$980.01	$980.00	$980.10