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	$215.96	11.486%	$240.7652	$240.77	$240.75	$240.80
Purchase #2	$88.83	12.324%	$99.7774	$99.78	$99.80	$99.80
Purchase #3	$98.91	13.156%	$111.9226	$111.92	$111.90	$111.90
Purchase #4	$236.61	3.527%	$244.9552	$244.96	$244.95	$245.00
Purchase #5	$234.66	9.406%	$256.7321	$256.73	$256.75	$256.70
Purchase #6	$244.25	5.113%	$256.7385	$256.74	$256.75	$256.70
Purchase #7	$235.37	5.244%	$247.7128	$247.71	$247.70	$247.70
7 purchase totals =	$1,354.59		$1,458.6038	$1,458.61	$1,458.60	$1,458.60