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	$203.77	4.858%	$213.6691	$213.67	$213.65	$213.70
Purchase #2	$10.40	4.612%	$10.8796	$10.88	$10.90	$10.90
Purchase #3	$131.72	4.134%	$137.1653	$137.17	$137.15	$137.20
Purchase #4	$13.57	6.491%	$14.4508	$14.45	$14.45	$14.50
Purchase #5	$46.66	5.793%	$49.363	$49.36	$49.35	$49.40
Purchase #6	$173.61	8.536%	$188.4293	$188.43	$188.45	$188.40
Purchase #7	$229.79	11.348%	$255.8666	$255.87	$255.85	$255.90
7 purchase totals =	$809.52		$869.8237	$869.83	$869.80	$870.00