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	$192.67	3.755%	$199.9048	$199.90	$199.90	$199.90
Purchase #2	$13.66	11.785%	$15.2698	$15.27	$15.25	$15.30
Purchase #3	$133.40	4.757%	$139.7458	$139.75	$139.75	$139.70
Purchase #4	$196.53	6.481%	$209.2671	$209.27	$209.25	$209.30
Purchase #5	$32.90	5.302%	$34.6444	$34.64	$34.65	$34.60
Purchase #6	$140.59	4.170%	$146.4526	$146.45	$146.45	$146.50
Purchase #7	$211.52	5.342%	$222.8194	$222.82	$222.80	$222.80
7 purchase totals =	$921.27		$968.1039	$968.10	$968.05	$968.10