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	$191.38	13.296%	$216.8259	$216.83	$216.85	$216.80
Purchase #2	$196.87	13.107%	$222.6738	$222.67	$222.65	$222.70
Purchase #3	$94.90	5.472%	$100.0929	$100.09	$100.10	$100.10
Purchase #4	$44.74	4.153%	$46.5981	$46.60	$46.60	$46.60
Purchase #5	$109.96	9.176%	$120.0499	$120.05	$120.05	$120.00
Purchase #6	$20.59	7.647%	$22.1645	$22.16	$22.15	$22.20
Purchase #7	$128.89	7.674%	$138.781	$138.78	$138.80	$138.80
7 purchase totals =	$787.33		$867.1861	$867.18	$867.20	$867.20