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	$141.36	12.232%	$158.6512	$158.65	$158.65	$158.70
Purchase #2	$62.40	10.131%	$68.7217	$68.72	$68.70	$68.70
Purchase #3	$40.49	9.211%	$44.2195	$44.22	$44.20	$44.20
Purchase #4	$90.40	11.606%	$100.8918	$100.89	$100.90	$100.90
Purchase #5	$34.30	3.387%	$35.4617	$35.46	$35.45	$35.50
Purchase #6	$150.66	6.482%	$160.4258	$160.43	$160.45	$160.40
Purchase #7	$46.96	4.136%	$48.9023	$48.90	$48.90	$48.90
7 purchase totals =	$566.57		$617.2740	$617.27	$617.25	$617.30