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	$153.90	9.626%	$168.7144	$168.71	$168.70	$168.70
Purchase #2	$167.78	13.262%	$190.031	$190.03	$190.05	$190.00
Purchase #3	$46.93	4.789%	$49.1775	$49.18	$49.20	$49.20
Purchase #4	$78.92	8.558%	$85.674	$85.67	$85.65	$85.70
Purchase #5	$91.38	4.460%	$95.4555	$95.46	$95.45	$95.50
Purchase #6	$193.45	8.828%	$210.5278	$210.53	$210.55	$210.50
Purchase #7	$33.98	8.698%	$36.9356	$36.94	$36.95	$36.90
7 purchase totals =	$766.34		$836.5158	$836.52	$836.55	$836.50