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	$114.34	11.570%	$127.5691	$127.57	$127.55	$127.60
Purchase #2	$206.78	11.744%	$231.0642	$231.06	$231.05	$231.10
Purchase #3	$188.97	9.509%	$206.9392	$206.94	$206.95	$206.90
Purchase #4	$98.69	13.146%	$111.6638	$111.66	$111.65	$111.70
Purchase #5	$91.88	4.395%	$95.9181	$95.92	$95.90	$95.90
Purchase #6	$34.69	10.624%	$38.3755	$38.38	$38.40	$38.40
Purchase #7	$51.95	8.699%	$56.4691	$56.47	$56.45	$56.50
7 purchase totals =	$787.30		$867.9990	$868.00	$867.95	$868.10