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	$118.57	6.769%	$126.596	$126.60	$126.60	$126.60
Purchase #2	$11.26	13.857%	$12.8203	$12.82	$12.80	$12.80
Purchase #3	$50.60	4.262%	$52.7566	$52.76	$52.75	$52.80
Purchase #4	$79.86	13.138%	$90.352	$90.35	$90.35	$90.40
Purchase #5	$37.91	6.851%	$40.5072	$40.51	$40.50	$40.50
Purchase #6	$79.48	10.641%	$87.9375	$87.94	$87.95	$87.90
Purchase #7	$143.42	5.347%	$151.0887	$151.09	$151.10	$151.10
7 purchase totals =	$521.10		$562.0583	$562.07	$562.05	$562.10