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	$39.97	4.124%	$41.6184	$41.62	$41.60	$41.60
Purchase #2	$57.50	3.382%	$59.4447	$59.44	$59.45	$59.40
Purchase #3	$85.91	4.863%	$90.0878	$90.09	$90.10	$90.10
Purchase #4	$132.98	6.291%	$141.3458	$141.35	$141.35	$141.30
Purchase #5	$207.91	12.554%	$234.011	$234.01	$234.00	$234.00
Purchase #6	$108.54	4.336%	$113.2463	$113.25	$113.25	$113.20
Purchase #7	$222.25	6.837%	$237.4452	$237.45	$237.45	$237.40
7 purchase totals =	$855.06		$917.1992	$917.21	$917.20	$917.00