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	$56.73	10.195%	$62.5136	$62.51	$62.50	$62.50
Purchase #2	$10.34	4.825%	$10.8389	$10.84	$10.85	$10.80
Purchase #3	$112.93	3.456%	$116.8329	$116.83	$116.85	$116.80
Purchase #4	$62.54	4.756%	$65.5144	$65.51	$65.50	$65.50
Purchase #5	$86.50	4.154%	$90.0932	$90.09	$90.10	$90.10
Purchase #6	$182.89	11.841%	$204.546	$204.55	$204.55	$204.50
Purchase #7	$246.57	3.874%	$256.1221	$256.12	$256.10	$256.10
7 purchase totals =	$758.50		$806.4611	$806.45	$806.45	$806.30