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	$16.94	13.305%	$19.1939	$19.19	$19.20	$19.20
Purchase #2	$85.62	11.516%	$95.48	$95.48	$95.50	$95.50
Purchase #3	$18.99	7.798%	$20.4708	$20.47	$20.45	$20.50
Purchase #4	$35.28	11.340%	$39.2808	$39.28	$39.30	$39.30
Purchase #5	$145.85	6.256%	$154.9744	$154.97	$154.95	$155.00
Purchase #6	$80.81	5.314%	$85.1042	$85.10	$85.10	$85.10
Purchase #7	$111.33	6.382%	$118.4351	$118.44	$118.45	$118.40
7 purchase totals =	$494.82		$532.9392	$532.93	$532.95	$533.00