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	$100.60	11.525%	$112.1942	$112.19	$112.20	$112.20
Purchase #2	$87.71	6.674%	$93.5638	$93.56	$93.55	$93.60
Purchase #3	$151.37	13.342%	$171.5658	$171.57	$171.55	$171.60
Purchase #4	$22.83	5.757%	$24.1443	$24.14	$24.15	$24.10
Purchase #5	$82.31	11.386%	$91.6818	$91.68	$91.70	$91.70
Purchase #6	$109.94	3.127%	$113.3778	$113.38	$113.40	$113.40
Purchase #7	$125.88	4.593%	$131.6617	$131.66	$131.65	$131.70
7 purchase totals =	$680.64		$738.1894	$738.18	$738.20	$738.30