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	$239.42	9.611%	$262.4307	$262.43	$262.45	$262.40
Purchase #2	$82.55	11.613%	$92.1365	$92.14	$92.15	$92.10
Purchase #3	$92.86	12.654%	$104.6105	$104.61	$104.60	$104.60
Purchase #4	$208.98	5.163%	$219.7696	$219.77	$219.75	$219.80
Purchase #5	$143.29	5.509%	$151.1838	$151.18	$151.20	$151.20
Purchase #6	$172.78	8.868%	$188.1021	$188.10	$188.10	$188.10
Purchase #7	$59.87	6.120%	$63.534	$63.53	$63.55	$63.50
7 purchase totals =	$999.75		$1,081.7672	$1,081.76	$1,081.80	$1,081.70