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	$92.72	12.204%	$104.0355	$104.04	$104.05	$104.00
Purchase #2	$215.81	10.172%	$237.7622	$237.76	$237.75	$237.80
Purchase #3	$9.83	5.678%	$10.3881	$10.39	$10.40	$10.40
Purchase #4	$80.58	6.822%	$86.0772	$86.08	$86.10	$86.10
Purchase #5	$83.53	8.791%	$90.8731	$90.87	$90.85	$90.90
Purchase #6	$77.38	5.463%	$81.6073	$81.61	$81.60	$81.60
Purchase #7	$187.71	12.103%	$210.4285	$210.43	$210.45	$210.40
7 purchase totals =	$747.56		$821.1719	$821.18	$821.20	$821.20