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	$109.27	3.311%	$112.8879	$112.89	$112.90	$112.90
Purchase #2	$166.99	4.195%	$173.9952	$174.00	$174.00	$174.00
Purchase #3	$99.87	5.835%	$105.6974	$105.70	$105.70	$105.70
Purchase #4	$117.52	3.697%	$121.8647	$121.86	$121.85	$121.90
Purchase #5	$86.53	5.733%	$91.4908	$91.49	$91.50	$91.50
Purchase #6	$43.66	10.800%	$48.3753	$48.38	$48.40	$48.40
Purchase #7	$40.75	3.738%	$42.2732	$42.27	$42.25	$42.30
7 purchase totals =	$664.59		$696.5845	$696.59	$696.60	$696.70