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	$66.35	8.594%	$72.0521	$72.05	$72.05	$72.10
Purchase #2	$239.53	10.152%	$263.8471	$263.85	$263.85	$263.80
Purchase #3	$103.61	4.670%	$108.4486	$108.45	$108.45	$108.40
Purchase #4	$20.44	5.169%	$21.4965	$21.50	$21.50	$21.50
Purchase #5	$50.72	3.249%	$52.3679	$52.37	$52.35	$52.40
Purchase #6	$50.38	6.527%	$53.6683	$53.67	$53.65	$53.70
Purchase #7	$145.35	4.637%	$152.0899	$152.09	$152.10	$152.10
7 purchase totals =	$676.38		$723.9704	$723.98	$723.95	$724.00