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	$229.34	11.494%	$255.7003	$255.70	$255.70	$255.70
Purchase #2	$143.38	10.545%	$158.4994	$158.50	$158.50	$158.50
Purchase #3	$37.42	7.622%	$40.2722	$40.27	$40.25	$40.30
Purchase #4	$19.88	8.744%	$21.6183	$21.62	$21.60	$21.60
Purchase #5	$112.86	9.700%	$123.8074	$123.81	$123.80	$123.80
Purchase #6	$174.66	6.262%	$185.5972	$185.60	$185.60	$185.60
Purchase #7	$71.66	12.433%	$80.5695	$80.57	$80.55	$80.60
7 purchase totals =	$789.20		$866.0643	$866.07	$866.00	$866.10