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	$200.65	11.517%	$223.7589	$223.76	$223.75	$223.80
Purchase #2	$127.88	11.859%	$143.0453	$143.05	$143.05	$143.00
Purchase #3	$40.61	12.533%	$45.6997	$45.70	$45.70	$45.70
Purchase #4	$57.27	10.697%	$63.3962	$63.40	$63.40	$63.40
Purchase #5	$90.70	9.779%	$99.5696	$99.57	$99.55	$99.60
Purchase #6	$226.61	4.381%	$236.5378	$236.54	$236.55	$236.50
Purchase #7	$129.86	13.782%	$147.7573	$147.76	$147.75	$147.80
7 purchase totals =	$873.58		$959.7648	$959.78	$959.75	$959.80