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	$60.53	9.260%	$66.1351	$66.14	$66.15	$66.10
Purchase #2	$196.42	13.237%	$222.4201	$222.42	$222.40	$222.40
Purchase #3	$33.33	6.750%	$35.5798	$35.58	$35.60	$35.60
Purchase #4	$146.45	4.468%	$152.9934	$152.99	$153.00	$153.00
Purchase #5	$159.66	8.263%	$172.8527	$172.85	$172.85	$172.90
Purchase #6	$227.94	3.868%	$236.7567	$236.76	$236.75	$236.80
Purchase #7	$143.35	13.584%	$162.8227	$162.82	$162.80	$162.80
7 purchase totals =	$967.68		$1,049.5605	$1,049.56	$1,049.55	$1,049.60