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	$22.34	13.658%	$25.3912	$25.39	$25.40	$25.40
Purchase #2	$31.96	11.724%	$35.707	$35.71	$35.70	$35.70
Purchase #3	$77.28	8.548%	$83.8859	$83.89	$83.90	$83.90
Purchase #4	$145.57	11.204%	$161.8797	$161.88	$161.90	$161.90
Purchase #5	$240.56	7.497%	$258.5948	$258.59	$258.60	$258.60
Purchase #6	$132.27	8.429%	$143.419	$143.42	$143.40	$143.40
Purchase #7	$49.51	12.322%	$55.6106	$55.61	$55.60	$55.60
7 purchase totals =	$699.49		$764.4882	$764.49	$764.50	$764.50