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	$69.36	7.370%	$74.4718	$74.47	$74.45	$74.50
Purchase #2	$10.66	7.772%	$11.4885	$11.49	$11.50	$11.50
Purchase #3	$231.83	4.326%	$241.859	$241.86	$241.85	$241.90
Purchase #4	$70.92	10.697%	$78.5063	$78.51	$78.50	$78.50
Purchase #5	$11.72	7.652%	$12.6168	$12.62	$12.60	$12.60
Purchase #6	$236.51	4.189%	$246.4174	$246.42	$246.40	$246.40
Purchase #7	$203.76	11.404%	$226.9968	$227.00	$227.00	$227.00
7 purchase totals =	$834.76		$892.3566	$892.37	$892.30	$892.40