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	$117.94	4.564%	$123.3228	$123.32	$123.30	$123.30
Purchase #2	$109.87	11.821%	$122.8577	$122.86	$122.85	$122.90
Purchase #3	$66.35	4.185%	$69.1267	$69.13	$69.15	$69.10
Purchase #4	$98.55	9.738%	$108.1468	$108.15	$108.15	$108.10
Purchase #5	$107.70	8.254%	$116.5896	$116.59	$116.60	$116.60
Purchase #6	$38.82	5.859%	$41.0945	$41.09	$41.10	$41.10
Purchase #7	$132.89	7.111%	$142.3398	$142.34	$142.35	$142.30
7 purchase totals =	$672.12		$723.4779	$723.48	$723.50	$723.40