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	$30.26	10.204%	$33.3477	$33.35	$33.35	$33.30
Purchase #2	$236.49	4.419%	$246.9405	$246.94	$246.95	$246.90
Purchase #3	$11.69	4.237%	$12.1853	$12.19	$12.20	$12.20
Purchase #4	$114.25	11.613%	$127.5179	$127.52	$127.50	$127.50
Purchase #5	$205.25	12.784%	$231.4892	$231.49	$231.50	$231.50
Purchase #6	$227.82	3.582%	$235.9805	$235.98	$236.00	$236.00
Purchase #7	$69.84	12.562%	$78.6133	$78.61	$78.60	$78.60
7 purchase totals =	$895.60		$966.0744	$966.08	$966.10	$966.00