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	$163.83	5.176%	$172.3098	$172.31	$172.30	$172.30
Purchase #2	$31.90	9.245%	$34.8492	$34.85	$34.85	$34.80
Purchase #3	$129.67	7.565%	$139.4795	$139.48	$139.50	$139.50
Purchase #4	$124.99	6.405%	$132.9956	$133.00	$133.00	$133.00
Purchase #5	$95.45	10.818%	$105.7758	$105.78	$105.80	$105.80
Purchase #6	$190.87	10.595%	$211.0927	$211.09	$211.10	$211.10
Purchase #7	$239.58	8.485%	$259.9084	$259.91	$259.90	$259.90
7 purchase totals =	$976.29		$1,056.4110	$1,056.42	$1,056.45	$1,056.40