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	$172.93	13.649%	$196.5332	$196.53	$196.55	$196.50
Purchase #2	$154.48	12.596%	$173.9383	$173.94	$173.95	$173.90
Purchase #3	$38.90	8.781%	$42.3158	$42.32	$42.30	$42.30
Purchase #4	$53.30	11.545%	$59.4535	$59.45	$59.45	$59.50
Purchase #5	$36.97	8.452%	$40.0947	$40.09	$40.10	$40.10
Purchase #6	$34.90	5.169%	$36.704	$36.70	$36.70	$36.70
Purchase #7	$187.32	11.338%	$208.5583	$208.56	$208.55	$208.60
7 purchase totals =	$678.80		$757.5978	$757.59	$757.60	$757.60