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	$200.93	9.318%	$219.6527	$219.65	$219.65	$219.70
Purchase #2	$192.72	11.150%	$214.2083	$214.21	$214.20	$214.20
Purchase #3	$54.66	13.703%	$62.1501	$62.15	$62.15	$62.20
Purchase #4	$247.45	3.692%	$256.5859	$256.59	$256.60	$256.60
Purchase #5	$26.86	13.368%	$30.4506	$30.45	$30.45	$30.50
Purchase #6	$41.70	4.551%	$43.5978	$43.60	$43.60	$43.60
Purchase #7	$91.72	13.323%	$103.9399	$103.94	$103.95	$103.90
7 purchase totals =	$856.04		$930.5853	$930.59	$930.60	$930.70