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	$211.78	9.497%	$231.8927	$231.89	$231.90	$231.90
Purchase #2	$71.62	12.411%	$80.5088	$80.51	$80.50	$80.50
Purchase #3	$153.76	7.699%	$165.598	$165.60	$165.60	$165.60
Purchase #4	$118.89	11.105%	$132.0927	$132.09	$132.10	$132.10
Purchase #5	$104.30	6.730%	$111.3194	$111.32	$111.30	$111.30
Purchase #6	$144.92	12.744%	$163.3886	$163.39	$163.40	$163.40
Purchase #7	$10.75	10.202%	$11.8467	$11.85	$11.85	$11.80
7 purchase totals =	$816.02		$896.6469	$896.65	$896.65	$896.60