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	$141.35	4.773%	$148.0966	$148.10	$148.10	$148.10
Purchase #2	$151.82	13.844%	$172.838	$172.84	$172.85	$172.80
Purchase #3	$88.45	6.198%	$93.9321	$93.93	$93.95	$93.90
Purchase #4	$48.66	5.582%	$51.3762	$51.38	$51.40	$51.40
Purchase #5	$237.51	13.520%	$269.6214	$269.62	$269.60	$269.60
Purchase #6	$224.47	13.346%	$254.4278	$254.43	$254.45	$254.40
Purchase #7	$37.81	6.830%	$40.3924	$40.39	$40.40	$40.40
7 purchase totals =	$930.07		$1,030.6845	$1,030.69	$1,030.75	$1,030.60