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	$59.85	6.111%	$63.5074	$63.51	$63.50	$63.50
Purchase #2	$137.43	10.684%	$152.113	$152.11	$152.10	$152.10
Purchase #3	$102.62	13.693%	$116.6718	$116.67	$116.65	$116.70
Purchase #4	$48.78	4.839%	$51.1405	$51.14	$51.15	$51.10
Purchase #5	$38.44	10.679%	$42.545	$42.55	$42.55	$42.50
Purchase #6	$192.41	3.711%	$199.5503	$199.55	$199.55	$199.60
Purchase #7	$70.92	10.772%	$78.5595	$78.56	$78.55	$78.60
7 purchase totals =	$650.45		$704.0875	$704.09	$704.05	$704.10