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	$126.36	13.235%	$143.0837	$143.08	$143.10	$143.10
Purchase #2	$95.55	5.395%	$100.7049	$100.70	$100.70	$100.70
Purchase #3	$72.77	8.189%	$78.7291	$78.73	$78.75	$78.70
Purchase #4	$199.68	8.796%	$217.2439	$217.24	$217.25	$217.20
Purchase #5	$223.61	12.293%	$251.0984	$251.10	$251.10	$251.10
Purchase #6	$88.41	13.786%	$100.5982	$100.60	$100.60	$100.60
Purchase #7	$66.56	6.754%	$71.0555	$71.06	$71.05	$71.10
7 purchase totals =	$872.94		$962.5137	$962.51	$962.55	$962.50