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	$140.28	13.510%	$159.2318	$159.23	$159.25	$159.20
Purchase #2	$179.78	9.443%	$196.7566	$196.76	$196.75	$196.80
Purchase #3	$217.64	11.733%	$243.1757	$243.18	$243.20	$243.20
Purchase #4	$116.37	4.724%	$121.8673	$121.87	$121.85	$121.90
Purchase #5	$150.40	10.849%	$166.7169	$166.72	$166.70	$166.70
Purchase #6	$117.50	5.433%	$123.8838	$123.88	$123.90	$123.90
Purchase #7	$86.91	9.769%	$95.4002	$95.40	$95.40	$95.40
7 purchase totals =	$1,008.88		$1,107.0323	$1,107.04	$1,107.05	$1,107.10