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	$245.90	6.807%	$262.6384	$262.64	$262.65	$262.60
Purchase #2	$195.59	11.404%	$217.8951	$217.90	$217.90	$217.90
Purchase #3	$153.45	8.740%	$166.8615	$166.86	$166.85	$166.90
Purchase #4	$18.50	5.724%	$19.5589	$19.56	$19.55	$19.60
Purchase #5	$43.98	3.463%	$45.503	$45.50	$45.50	$45.50
Purchase #6	$17.40	7.246%	$18.6608	$18.66	$18.65	$18.70
Purchase #7	$126.99	4.644%	$132.8874	$132.89	$132.90	$132.90
7 purchase totals =	$801.81		$864.0051	$864.01	$864.00	$864.10