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	$64.27	7.368%	$69.0054	$69.01	$69.00	$69.00
Purchase #2	$87.80	3.378%	$90.7659	$90.77	$90.75	$90.80
Purchase #3	$238.28	6.606%	$254.0208	$254.02	$254.00	$254.00
Purchase #4	$132.53	8.587%	$143.9104	$143.91	$143.90	$143.90
Purchase #5	$14.95	5.828%	$15.8213	$15.82	$15.80	$15.80
Purchase #6	$161.60	3.700%	$167.5792	$167.58	$167.60	$167.60
Purchase #7	$101.80	9.104%	$111.0679	$111.07	$111.05	$111.10
7 purchase totals =	$801.23		$852.1709	$852.18	$852.10	$852.20