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	$73.76	13.849%	$83.975	$83.98	$84.00	$84.00
Purchase #2	$69.34	6.237%	$73.6647	$73.66	$73.65	$73.70
Purchase #3	$164.32	8.363%	$178.0621	$178.06	$178.05	$178.10
Purchase #4	$29.92	11.528%	$33.3692	$33.37	$33.35	$33.40
Purchase #5	$65.85	4.559%	$68.8521	$68.85	$68.85	$68.90
Purchase #6	$89.89	6.327%	$95.5773	$95.58	$95.60	$95.60
Purchase #7	$33.92	11.367%	$37.7757	$37.78	$37.80	$37.80
7 purchase totals =	$527.00		$571.2761	$571.28	$571.30	$571.50