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	$140.83	8.312%	$152.5358	$152.54	$152.55	$152.50
Purchase #2	$112.28	5.451%	$118.4004	$118.40	$118.40	$118.40
Purchase #3	$59.46	6.554%	$63.357	$63.36	$63.35	$63.40
Purchase #4	$175.95	10.739%	$194.8453	$194.85	$194.85	$194.80
Purchase #5	$41.47	3.439%	$42.8962	$42.90	$42.90	$42.90
Purchase #6	$165.45	11.853%	$185.0608	$185.06	$185.05	$185.10
Purchase #7	$178.84	13.161%	$202.3771	$202.38	$202.40	$202.40
7 purchase totals =	$874.28		$959.4726	$959.49	$959.50	$959.50