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	$10.34	10.188%	$11.3934	$11.39	$11.40	$11.40
Purchase #2	$142.35	6.490%	$151.5885	$151.59	$151.60	$151.60
Purchase #3	$34.46	10.200%	$37.9749	$37.97	$37.95	$38.00
Purchase #4	$18.41	4.216%	$19.1862	$19.19	$19.20	$19.20
Purchase #5	$171.52	11.117%	$190.5879	$190.59	$190.60	$190.60
Purchase #6	$99.49	13.485%	$112.9062	$112.91	$112.90	$112.90
Purchase #7	$77.80	5.176%	$81.8269	$81.83	$81.85	$81.80
7 purchase totals =	$554.37		$605.4640	$605.47	$605.50	$605.50