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	$194.52	10.457%	$214.861	$214.86	$214.85	$214.90
Purchase #2	$103.51	7.575%	$111.3509	$111.35	$111.35	$111.40
Purchase #3	$60.27	11.168%	$67.001	$67.00	$67.00	$67.00
Purchase #4	$126.91	4.278%	$132.3392	$132.34	$132.35	$132.30
Purchase #5	$133.49	7.671%	$143.73	$143.73	$143.75	$143.70
Purchase #6	$178.47	11.851%	$199.6205	$199.62	$199.60	$199.60
Purchase #7	$66.49	8.155%	$71.9123	$71.91	$71.90	$71.90
7 purchase totals =	$863.66		$940.8149	$940.81	$940.80	$940.80