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	$52.65	5.804%	$55.7058	$55.71	$55.70	$55.70
Purchase #2	$11.29	11.305%	$12.5663	$12.57	$12.55	$12.60
Purchase #3	$56.78	5.724%	$60.0301	$60.03	$60.05	$60.00
Purchase #4	$137.30	4.621%	$143.6446	$143.64	$143.65	$143.60
Purchase #5	$98.45	11.236%	$109.5118	$109.51	$109.50	$109.50
Purchase #6	$122.67	3.194%	$126.5881	$126.59	$126.60	$126.60
Purchase #7	$172.53	9.844%	$189.5139	$189.51	$189.50	$189.50
7 purchase totals =	$651.67		$697.5606	$697.56	$697.55	$697.50