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	$195.66	12.445%	$220.0099	$220.01	$220.00	$220.00
Purchase #2	$68.34	6.575%	$72.8334	$72.83	$72.85	$72.80
Purchase #3	$97.60	5.707%	$103.17	$103.17	$103.15	$103.20
Purchase #4	$83.89	13.821%	$95.4844	$95.48	$95.50	$95.50
Purchase #5	$62.53	6.342%	$66.4957	$66.50	$66.50	$66.50
Purchase #6	$125.43	13.788%	$142.7243	$142.72	$142.70	$142.70
Purchase #7	$153.34	10.242%	$169.0451	$169.05	$169.05	$169.00
7 purchase totals =	$786.79		$869.7628	$869.76	$869.75	$869.70