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	$231.96	12.724%	$261.4746	$261.47	$261.45	$261.50
Purchase #2	$140.60	12.679%	$158.4267	$158.43	$158.45	$158.40
Purchase #3	$161.29	6.859%	$172.3529	$172.35	$172.35	$172.40
Purchase #4	$127.26	9.370%	$139.1843	$139.18	$139.20	$139.20
Purchase #5	$130.56	6.570%	$139.1378	$139.14	$139.15	$139.10
Purchase #6	$136.72	6.501%	$145.6082	$145.61	$145.60	$145.60
Purchase #7	$68.88	4.126%	$71.722	$71.72	$71.70	$71.70
7 purchase totals =	$997.27		$1,087.9065	$1,087.90	$1,087.90	$1,087.90