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	$157.54	9.620%	$172.6953	$172.70	$172.70	$172.70
Purchase #2	$100.54	13.660%	$114.2738	$114.27	$114.25	$114.30
Purchase #3	$242.49	11.797%	$271.0965	$271.10	$271.10	$271.10
Purchase #4	$18.96	12.575%	$21.3442	$21.34	$21.35	$21.30
Purchase #5	$235.43	9.119%	$256.8989	$256.90	$256.90	$256.90
Purchase #6	$10.46	12.126%	$11.7284	$11.73	$11.75	$11.70
Purchase #7	$202.66	6.379%	$215.5877	$215.59	$215.60	$215.60
7 purchase totals =	$968.08		$1,063.6248	$1,063.63	$1,063.65	$1,063.60