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	$78.47	7.696%	$84.5091	$84.51	$84.50	$84.50
Purchase #2	$25.75	3.185%	$26.5701	$26.57	$26.55	$26.60
Purchase #3	$94.37	11.771%	$105.4783	$105.48	$105.50	$105.50
Purchase #4	$172.77	10.322%	$190.6033	$190.60	$190.60	$190.60
Purchase #5	$120.53	10.249%	$132.8831	$132.88	$132.90	$132.90
Purchase #6	$133.43	13.208%	$151.0534	$151.05	$151.05	$151.10
Purchase #7	$240.69	13.487%	$273.1519	$273.15	$273.15	$273.20
7 purchase totals =	$866.01		$964.2492	$964.24	$964.25	$964.40