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	$14.95	12.811%	$16.8652	$16.87	$16.85	$16.90
Purchase #2	$16.38	13.437%	$18.581	$18.58	$18.60	$18.60
Purchase #3	$70.41	10.797%	$78.0122	$78.01	$78.00	$78.00
Purchase #4	$99.52	4.275%	$103.7745	$103.77	$103.75	$103.80
Purchase #5	$79.77	11.434%	$88.8909	$88.89	$88.90	$88.90
Purchase #6	$102.47	11.108%	$113.8524	$113.85	$113.85	$113.90
Purchase #7	$28.76	11.615%	$32.1005	$32.10	$32.10	$32.10
7 purchase totals =	$412.26		$452.0767	$452.07	$452.05	$452.20