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	$59.64	4.701%	$62.4437	$62.44	$62.45	$62.40
Purchase #2	$237.49	4.205%	$247.4765	$247.48	$247.50	$247.50
Purchase #3	$242.45	5.509%	$255.8066	$255.81	$255.80	$255.80
Purchase #4	$34.37	12.622%	$38.7082	$38.71	$38.70	$38.70
Purchase #5	$94.55	5.798%	$100.032	$100.03	$100.05	$100.00
Purchase #6	$220.28	8.466%	$238.9289	$238.93	$238.95	$238.90
Purchase #7	$182.87	7.434%	$196.4646	$196.46	$196.45	$196.50
7 purchase totals =	$1,071.65		$1,139.8605	$1,139.86	$1,139.90	$1,139.80