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	$184.52	13.509%	$209.4468	$209.45	$209.45	$209.40
Purchase #2	$126.72	8.504%	$137.4963	$137.50	$137.50	$137.50
Purchase #3	$18.38	13.683%	$20.8949	$20.89	$20.90	$20.90
Purchase #4	$120.75	12.154%	$135.426	$135.43	$135.45	$135.40
Purchase #5	$54.48	4.212%	$56.7747	$56.77	$56.75	$56.80
Purchase #6	$87.50	11.113%	$97.2239	$97.22	$97.20	$97.20
Purchase #7	$90.55	13.531%	$102.8023	$102.80	$102.80	$102.80
7 purchase totals =	$682.90		$760.0649	$760.06	$760.05	$760.00