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	$67.71	13.158%	$76.6193	$76.62	$76.60	$76.60
Purchase #2	$64.61	11.856%	$72.2702	$72.27	$72.25	$72.30
Purchase #3	$22.26	4.266%	$23.2096	$23.21	$23.20	$23.20
Purchase #4	$159.70	8.683%	$173.5668	$173.57	$173.55	$173.60
Purchase #5	$249.51	12.290%	$280.1748	$280.17	$280.15	$280.20
Purchase #6	$93.39	12.526%	$105.088	$105.09	$105.10	$105.10
Purchase #7	$162.86	3.814%	$169.0715	$169.07	$169.05	$169.10
7 purchase totals =	$820.04		$900.0002	$900.00	$899.90	$900.10