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	$127.91	11.658%	$142.8217	$142.82	$142.80	$142.80
Purchase #2	$63.83	4.131%	$66.4668	$66.47	$66.45	$66.50
Purchase #3	$8.72	13.461%	$9.8938	$9.89	$9.90	$9.90
Purchase #4	$92.50	10.733%	$102.428	$102.43	$102.45	$102.40
Purchase #5	$175.42	6.863%	$187.4591	$187.46	$187.45	$187.50
Purchase #6	$126.37	10.683%	$139.8701	$139.87	$139.85	$139.90
Purchase #7	$248.32	4.646%	$259.8569	$259.86	$259.85	$259.90
7 purchase totals =	$843.07		$908.7964	$908.80	$908.75	$908.90