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	$58.38	13.731%	$66.3962	$66.40	$66.40	$66.40
Purchase #2	$242.62	8.772%	$263.9026	$263.90	$263.90	$263.90
Purchase #3	$172.88	4.171%	$180.0908	$180.09	$180.10	$180.10
Purchase #4	$15.67	12.246%	$17.5889	$17.59	$17.60	$17.60
Purchase #5	$248.45	10.841%	$275.3845	$275.38	$275.40	$275.40
Purchase #6	$72.99	6.152%	$77.4803	$77.48	$77.50	$77.50
Purchase #7	$116.85	11.838%	$130.6827	$130.68	$130.70	$130.70
7 purchase totals =	$927.84		$1,011.5260	$1,011.52	$1,011.60	$1,011.60