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	$154.64	8.182%	$167.2926	$167.29	$167.30	$167.30
Purchase #2	$93.69	11.382%	$104.3538	$104.35	$104.35	$104.40
Purchase #3	$246.41	10.605%	$272.5418	$272.54	$272.55	$272.50
Purchase #4	$153.68	4.810%	$161.072	$161.07	$161.05	$161.10
Purchase #5	$46.90	3.698%	$48.6344	$48.63	$48.65	$48.60
Purchase #6	$152.35	5.520%	$160.7597	$160.76	$160.75	$160.80
Purchase #7	$172.26	10.600%	$190.5196	$190.52	$190.50	$190.50
7 purchase totals =	$1,019.93		$1,105.1739	$1,105.16	$1,105.15	$1,105.20