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	$216.34	5.188%	$227.5637	$227.56	$227.55	$227.60
Purchase #2	$143.86	3.849%	$149.3972	$149.40	$149.40	$149.40
Purchase #3	$224.48	8.734%	$244.0861	$244.09	$244.10	$244.10
Purchase #4	$80.93	6.104%	$85.87	$85.87	$85.85	$85.90
Purchase #5	$80.40	6.360%	$85.5134	$85.51	$85.50	$85.50
Purchase #6	$41.70	8.795%	$45.3675	$45.37	$45.35	$45.40
Purchase #7	$244.27	7.202%	$261.8623	$261.86	$261.85	$261.90
7 purchase totals =	$1,031.98		$1,099.6602	$1,099.66	$1,099.60	$1,099.80