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	$169.75	13.396%	$192.4897	$192.49	$192.50	$192.50
Purchase #2	$231.25	8.571%	$251.0704	$251.07	$251.05	$251.10
Purchase #3	$210.27	5.821%	$222.5098	$222.51	$222.50	$222.50
Purchase #4	$101.66	9.632%	$111.4519	$111.45	$111.45	$111.50
Purchase #5	$234.86	12.249%	$263.628	$263.63	$263.65	$263.60
Purchase #6	$110.34	6.417%	$117.4205	$117.42	$117.40	$117.40
Purchase #7	$100.62	13.538%	$114.2419	$114.24	$114.25	$114.20
7 purchase totals =	$1,158.75		$1,272.8122	$1,272.81	$1,272.80	$1,272.80