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	$238.66	11.434%	$265.9484	$265.95	$265.95	$265.90
Purchase #2	$10.79	9.516%	$11.8168	$11.82	$11.80	$11.80
Purchase #3	$124.88	6.363%	$132.8261	$132.83	$132.85	$132.80
Purchase #4	$226.84	6.568%	$241.7389	$241.74	$241.75	$241.70
Purchase #5	$117.32	5.257%	$123.4875	$123.49	$123.50	$123.50
Purchase #6	$142.30	5.462%	$150.0724	$150.07	$150.05	$150.10
Purchase #7	$136.97	10.189%	$150.9259	$150.93	$150.95	$150.90
7 purchase totals =	$997.76		$1,076.8160	$1,076.83	$1,076.85	$1,076.70