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	$67.76	6.830%	$72.388	$72.39	$72.40	$72.40
Purchase #2	$216.34	4.198%	$225.422	$225.42	$225.40	$225.40
Purchase #3	$205.52	6.371%	$218.6137	$218.61	$218.60	$218.60
Purchase #4	$106.26	10.676%	$117.6043	$117.60	$117.60	$117.60
Purchase #5	$127.63	13.750%	$145.1791	$145.18	$145.20	$145.20
Purchase #6	$208.32	12.103%	$233.533	$233.53	$233.55	$233.50
Purchase #7	$56.73	12.509%	$63.8264	$63.83	$63.85	$63.80
7 purchase totals =	$988.56		$1,076.5665	$1,076.56	$1,076.60	$1,076.50