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	$26.73	7.862%	$28.8315	$28.83	$28.85	$28.80
Purchase #2	$56.43	6.772%	$60.2514	$60.25	$60.25	$60.30
Purchase #3	$19.47	5.679%	$20.5757	$20.58	$20.60	$20.60
Purchase #4	$83.93	8.308%	$90.9029	$90.90	$90.90	$90.90
Purchase #5	$125.98	4.840%	$132.0774	$132.08	$132.10	$132.10
Purchase #6	$16.29	13.839%	$18.5444	$18.54	$18.55	$18.50
Purchase #7	$84.77	3.604%	$87.8251	$87.83	$87.85	$87.80
7 purchase totals =	$413.60		$439.0084	$439.01	$439.10	$439.00