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	$55.38	10.426%	$61.1539	$61.15	$61.15	$61.20
Purchase #2	$192.72	6.645%	$205.5262	$205.53	$205.55	$205.50
Purchase #3	$123.81	6.593%	$131.9728	$131.97	$131.95	$132.00
Purchase #4	$24.75	13.434%	$28.0749	$28.07	$28.05	$28.10
Purchase #5	$123.90	12.608%	$139.5213	$139.52	$139.50	$139.50
Purchase #6	$89.58	4.409%	$93.5296	$93.53	$93.55	$93.50
Purchase #7	$61.95	12.166%	$69.4868	$69.49	$69.50	$69.50
7 purchase totals =	$672.09		$729.2655	$729.26	$729.25	$729.30