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	$105.97	4.375%	$110.6062	$110.61	$110.60	$110.60
Purchase #2	$118.68	10.767%	$131.4583	$131.46	$131.45	$131.50
Purchase #3	$16.87	3.792%	$17.5097	$17.51	$17.50	$17.50
Purchase #4	$55.34	7.140%	$59.2913	$59.29	$59.30	$59.30
Purchase #5	$30.99	11.785%	$34.6422	$34.64	$34.65	$34.60
Purchase #6	$133.32	7.634%	$143.4976	$143.50	$143.50	$143.50
Purchase #7	$14.67	5.429%	$15.4664	$15.47	$15.45	$15.50
7 purchase totals =	$475.84		$512.4717	$512.48	$512.45	$512.50