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	$6.87	10.239%	$7.5734	$7.57	$7.55	$7.60
Purchase #2	$102.37	13.456%	$116.1449	$116.14	$116.15	$116.10
Purchase #3	$102.57	5.778%	$108.4965	$108.50	$108.50	$108.50
Purchase #4	$118.25	11.614%	$131.9836	$131.98	$132.00	$132.00
Purchase #5	$68.28	9.136%	$74.5181	$74.52	$74.50	$74.50
Purchase #6	$142.90	5.387%	$150.598	$150.60	$150.60	$150.60
Purchase #7	$246.69	3.460%	$255.2255	$255.23	$255.25	$255.20
7 purchase totals =	$787.93		$844.5400	$844.54	$844.55	$844.50