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	$217.66	9.677%	$238.723	$238.72	$238.70	$238.70
Purchase #2	$159.34	4.491%	$166.496	$166.50	$166.50	$166.50
Purchase #3	$196.66	6.231%	$208.9139	$208.91	$208.90	$208.90
Purchase #4	$58.63	6.748%	$62.5864	$62.59	$62.60	$62.60
Purchase #5	$141.66	11.471%	$157.9098	$157.91	$157.90	$157.90
Purchase #6	$138.34	9.333%	$151.2513	$151.25	$151.25	$151.30
Purchase #7	$12.45	10.720%	$13.7846	$13.78	$13.80	$13.80
7 purchase totals =	$924.74		$999.6650	$999.66	$999.65	$999.70