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	$190.50	11.863%	$213.099	$213.10	$213.10	$213.10
Purchase #2	$238.52	3.836%	$247.6696	$247.67	$247.65	$247.70
Purchase #3	$97.70	9.342%	$106.8271	$106.83	$106.85	$106.80
Purchase #4	$214.59	10.570%	$237.2722	$237.27	$237.25	$237.30
Purchase #5	$196.86	13.718%	$223.8653	$223.87	$223.85	$223.90
Purchase #6	$94.85	5.189%	$99.7718	$99.77	$99.75	$99.80
Purchase #7	$138.42	10.136%	$152.4503	$152.45	$152.45	$152.50
7 purchase totals =	$1,171.44		$1,280.9553	$1,280.96	$1,280.90	$1,281.10