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	$172.71	10.147%	$190.2349	$190.23	$190.25	$190.20
Purchase #2	$15.30	3.371%	$15.8158	$15.82	$15.80	$15.80
Purchase #3	$90.68	11.128%	$100.7709	$100.77	$100.75	$100.80
Purchase #4	$197.78	11.446%	$220.4179	$220.42	$220.40	$220.40
Purchase #5	$103.55	7.768%	$111.5938	$111.59	$111.60	$111.60
Purchase #6	$220.33	11.874%	$246.492	$246.49	$246.50	$246.50
Purchase #7	$242.32	4.845%	$254.0604	$254.06	$254.05	$254.10
7 purchase totals =	$1,042.67		$1,139.3857	$1,139.38	$1,139.35	$1,139.40