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	$104.72	12.832%	$118.1577	$118.16	$118.15	$118.20
Purchase #2	$244.95	4.804%	$256.7174	$256.72	$256.70	$256.70
Purchase #3	$11.87	3.393%	$12.2727	$12.27	$12.25	$12.30
Purchase #4	$116.45	6.407%	$123.911	$123.91	$123.90	$123.90
Purchase #5	$9.86	12.553%	$11.0977	$11.10	$11.10	$11.10
Purchase #6	$250.30	11.389%	$278.8067	$278.81	$278.80	$278.80
Purchase #7	$158.54	11.360%	$176.5501	$176.55	$176.55	$176.60
7 purchase totals =	$896.69		$977.5133	$977.52	$977.45	$977.60