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	$217.35	8.187%	$235.1444	$235.14	$235.15	$235.10
Purchase #2	$70.52	10.499%	$77.9239	$77.92	$77.90	$77.90
Purchase #3	$89.87	11.295%	$100.0208	$100.02	$100.00	$100.00
Purchase #4	$157.51	8.231%	$170.4746	$170.47	$170.45	$170.50
Purchase #5	$220.98	7.307%	$237.127	$237.13	$237.15	$237.10
Purchase #6	$237.89	10.145%	$262.0239	$262.02	$262.00	$262.00
Purchase #7	$185.89	3.750%	$192.8609	$192.86	$192.85	$192.90
7 purchase totals =	$1,180.01		$1,275.5755	$1,275.56	$1,275.50	$1,275.50