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	$176.27	13.194%	$199.5271	$199.53	$199.55	$199.50
Purchase #2	$120.99	13.869%	$137.7701	$137.77	$137.75	$137.80
Purchase #3	$109.39	9.823%	$120.1354	$120.14	$120.15	$120.10
Purchase #4	$38.81	3.178%	$40.0434	$40.04	$40.05	$40.00
Purchase #5	$145.39	4.615%	$152.0997	$152.10	$152.10	$152.10
Purchase #6	$44.86	8.715%	$48.7695	$48.77	$48.75	$48.80
Purchase #7	$99.46	4.668%	$104.1028	$104.10	$104.10	$104.10
7 purchase totals =	$735.17		$802.4480	$802.45	$802.45	$802.40