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	$112.63	13.149%	$127.4397	$127.44	$127.45	$127.40
Purchase #2	$176.80	13.405%	$200.5	$200.50	$200.50	$200.50
Purchase #3	$124.75	7.185%	$133.7133	$133.71	$133.70	$133.70
Purchase #4	$66.48	12.287%	$74.6484	$74.65	$74.65	$74.60
Purchase #5	$146.83	10.282%	$161.9271	$161.93	$161.95	$161.90
Purchase #6	$90.31	11.457%	$100.6568	$100.66	$100.65	$100.70
Purchase #7	$12.86	13.399%	$14.5831	$14.58	$14.60	$14.60
7 purchase totals =	$730.66		$813.4684	$813.47	$813.50	$813.40