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	$119.81	10.483%	$132.3697	$132.37	$132.35	$132.40
Purchase #2	$152.72	9.733%	$167.5842	$167.58	$167.60	$167.60
Purchase #3	$229.77	7.252%	$246.4329	$246.43	$246.45	$246.40
Purchase #4	$212.61	13.746%	$241.8354	$241.84	$241.85	$241.80
Purchase #5	$215.68	8.551%	$234.1228	$234.12	$234.10	$234.10
Purchase #6	$78.51	5.203%	$82.5949	$82.59	$82.60	$82.60
Purchase #7	$231.38	8.103%	$250.1287	$250.13	$250.15	$250.10
7 purchase totals =	$1,240.48		$1,355.0686	$1,355.06	$1,355.10	$1,355.00