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	$180.47	5.304%	$190.0421	$190.04	$190.05	$190.00
Purchase #2	$19.66	4.670%	$20.5781	$20.58	$20.60	$20.60
Purchase #3	$140.78	9.620%	$154.323	$154.32	$154.30	$154.30
Purchase #4	$232.52	8.162%	$251.4983	$251.50	$251.50	$251.50
Purchase #5	$188.86	4.773%	$197.8743	$197.87	$197.85	$197.90
Purchase #6	$105.42	10.807%	$116.8127	$116.81	$116.80	$116.80
Purchase #7	$88.86	12.638%	$100.0901	$100.09	$100.10	$100.10
7 purchase totals =	$956.57		$1,031.2186	$1,031.21	$1,031.20	$1,031.20