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	$49.65	9.602%	$54.4174	$54.42	$54.40	$54.40
Purchase #2	$138.61	8.495%	$150.3849	$150.38	$150.40	$150.40
Purchase #3	$99.82	13.588%	$113.3835	$113.38	$113.40	$113.40
Purchase #4	$213.90	9.609%	$234.4537	$234.45	$234.45	$234.50
Purchase #5	$89.95	5.119%	$94.5545	$94.55	$94.55	$94.60
Purchase #6	$116.81	9.553%	$127.9689	$127.97	$127.95	$128.00
Purchase #7	$148.61	6.243%	$157.8877	$157.89	$157.90	$157.90
7 purchase totals =	$857.35		$933.0506	$933.04	$933.05	$933.20