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	$68.54	3.733%	$71.0986	$71.10	$71.10	$71.10
Purchase #2	$18.43	13.480%	$20.9144	$20.91	$20.90	$20.90
Purchase #3	$227.65	4.308%	$237.4572	$237.46	$237.45	$237.50
Purchase #4	$231.40	10.586%	$255.896	$255.90	$255.90	$255.90
Purchase #5	$193.80	12.108%	$217.2653	$217.27	$217.25	$217.30
Purchase #6	$68.69	13.840%	$78.1967	$78.20	$78.20	$78.20
Purchase #7	$143.94	8.852%	$156.6816	$156.68	$156.70	$156.70
7 purchase totals =	$952.45		$1,037.5098	$1,037.52	$1,037.50	$1,037.60