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	$58.48	10.400%	$64.5619	$64.56	$64.55	$64.60
Purchase #2	$90.81	10.671%	$100.5003	$100.50	$100.50	$100.50
Purchase #3	$108.32	3.268%	$111.8599	$111.86	$111.85	$111.90
Purchase #4	$138.28	5.301%	$145.6102	$145.61	$145.60	$145.60
Purchase #5	$145.28	11.178%	$161.5194	$161.52	$161.50	$161.50
Purchase #6	$42.26	6.214%	$44.886	$44.89	$44.90	$44.90
Purchase #7	$223.57	12.746%	$252.0662	$252.07	$252.05	$252.10
7 purchase totals =	$807.00		$881.0039	$881.01	$880.95	$881.10