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	$59.66	9.711%	$65.4536	$65.45	$65.45	$65.50
Purchase #2	$145.81	9.777%	$160.0658	$160.07	$160.05	$160.10
Purchase #3	$192.27	10.284%	$212.043	$212.04	$212.05	$212.00
Purchase #4	$79.94	10.172%	$88.0715	$88.07	$88.05	$88.10
Purchase #5	$83.48	5.546%	$88.1098	$88.11	$88.10	$88.10
Purchase #6	$97.73	3.189%	$100.8466	$100.85	$100.85	$100.80
Purchase #7	$16.51	13.177%	$18.6855	$18.69	$18.70	$18.70
7 purchase totals =	$675.40		$733.2758	$733.28	$733.25	$733.30