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	$126.97	7.488%	$136.4775	$136.48	$136.50	$136.50
Purchase #2	$250.43	4.131%	$260.7753	$260.78	$260.80	$260.80
Purchase #3	$56.41	4.461%	$58.9265	$58.93	$58.95	$58.90
Purchase #4	$56.26	13.163%	$63.6655	$63.67	$63.65	$63.70
Purchase #5	$129.76	12.861%	$146.4484	$146.45	$146.45	$146.40
Purchase #6	$151.29	13.756%	$172.1015	$172.10	$172.10	$172.10
Purchase #7	$97.64	13.834%	$111.1475	$111.15	$111.15	$111.10
7 purchase totals =	$868.76		$949.5422	$949.56	$949.60	$949.50