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	$111.65	4.488%	$116.6609	$116.66	$116.65	$116.70
Purchase #2	$155.57	13.640%	$176.7897	$176.79	$176.80	$176.80
Purchase #3	$90.81	10.215%	$100.0862	$100.09	$100.10	$100.10
Purchase #4	$157.92	11.778%	$176.5198	$176.52	$176.50	$176.50
Purchase #5	$130.58	9.173%	$142.5581	$142.56	$142.55	$142.60
Purchase #6	$10.73	9.443%	$11.7432	$11.74	$11.75	$11.70
Purchase #7	$52.86	5.139%	$55.5765	$55.58	$55.60	$55.60
7 purchase totals =	$710.12		$779.9344	$779.94	$779.95	$780.00