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	$47.29	8.761%	$51.4331	$51.43	$51.45	$51.40
Purchase #2	$12.54	5.415%	$13.219	$13.22	$13.20	$13.20
Purchase #3	$158.66	8.782%	$172.5935	$172.59	$172.60	$172.60
Purchase #4	$21.87	12.443%	$24.5913	$24.59	$24.60	$24.60
Purchase #5	$116.36	10.599%	$128.693	$128.69	$128.70	$128.70
Purchase #6	$215.86	9.531%	$236.4336	$236.43	$236.45	$236.40
Purchase #7	$199.51	11.303%	$222.0606	$222.06	$222.05	$222.10
7 purchase totals =	$772.09		$849.0241	$849.01	$849.05	$849.00