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	$66.82	8.742%	$72.6614	$72.66	$72.65	$72.70
Purchase #2	$239.82	5.543%	$253.1132	$253.11	$253.10	$253.10
Purchase #3	$241.53	5.609%	$255.0774	$255.08	$255.10	$255.10
Purchase #4	$204.85	11.377%	$228.1558	$228.16	$228.15	$228.20
Purchase #5	$74.99	10.711%	$83.0222	$83.02	$83.00	$83.00
Purchase #6	$154.59	8.683%	$168.013	$168.01	$168.00	$168.00
Purchase #7	$186.28	13.526%	$211.4762	$211.48	$211.50	$211.50
7 purchase totals =	$1,168.88		$1,271.5192	$1,271.52	$1,271.50	$1,271.60