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	$125.32	4.554%	$131.0271	$131.03	$131.05	$131.00
Purchase #2	$21.81	10.723%	$24.1487	$24.15	$24.15	$24.10
Purchase #3	$71.90	6.353%	$76.4678	$76.47	$76.45	$76.50
Purchase #4	$62.94	10.619%	$69.6236	$69.62	$69.60	$69.60
Purchase #5	$127.27	12.411%	$143.0655	$143.07	$143.05	$143.10
Purchase #6	$20.69	4.475%	$21.6159	$21.62	$21.60	$21.60
Purchase #7	$21.69	10.162%	$23.8941	$23.89	$23.90	$23.90
7 purchase totals =	$451.62		$489.8427	$489.85	$489.80	$489.80