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	$228.82	8.534%	$248.3475	$248.35	$248.35	$248.30
Purchase #2	$174.64	10.204%	$192.4603	$192.46	$192.45	$192.50
Purchase #3	$239.60	4.109%	$249.4452	$249.45	$249.45	$249.40
Purchase #4	$81.55	7.417%	$87.5986	$87.60	$87.60	$87.60
Purchase #5	$127.26	9.732%	$139.6449	$139.64	$139.65	$139.60
Purchase #6	$39.83	6.603%	$42.46	$42.46	$42.45	$42.50
Purchase #7	$146.98	5.481%	$155.036	$155.04	$155.05	$155.00
7 purchase totals =	$1,038.68		$1,114.9925	$1,115.00	$1,115.00	$1,114.90