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	$198.53	12.604%	$223.5527	$223.55	$223.55	$223.60
Purchase #2	$102.50	9.763%	$112.5071	$112.51	$112.50	$112.50
Purchase #3	$162.76	6.545%	$173.4126	$173.41	$173.40	$173.40
Purchase #4	$77.83	4.797%	$81.5635	$81.56	$81.55	$81.60
Purchase #5	$29.87	12.502%	$33.6043	$33.60	$33.60	$33.60
Purchase #6	$239.49	6.631%	$255.3706	$255.37	$255.35	$255.40
Purchase #7	$76.35	9.874%	$83.8888	$83.89	$83.90	$83.90
7 purchase totals =	$887.33		$963.8996	$963.89	$963.85	$964.00