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	$140.77	9.462%	$154.0897	$154.09	$154.10	$154.10
Purchase #2	$192.46	13.211%	$217.8859	$217.89	$217.90	$217.90
Purchase #3	$40.50	7.175%	$43.4059	$43.41	$43.40	$43.40
Purchase #4	$223.27	7.151%	$239.236	$239.24	$239.25	$239.20
Purchase #5	$229.41	12.826%	$258.8341	$258.83	$258.85	$258.80
Purchase #6	$170.27	10.373%	$187.9321	$187.93	$187.95	$187.90
Purchase #7	$151.81	4.389%	$158.4729	$158.47	$158.45	$158.50
7 purchase totals =	$1,148.49		$1,259.8566	$1,259.86	$1,259.90	$1,259.80