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	$103.30	10.722%	$114.3758	$114.38	$114.40	$114.40
Purchase #2	$139.95	8.792%	$152.2544	$152.25	$152.25	$152.30
Purchase #3	$137.49	6.545%	$146.4887	$146.49	$146.50	$146.50
Purchase #4	$133.56	4.382%	$139.4126	$139.41	$139.40	$139.40
Purchase #5	$31.45	12.126%	$35.2636	$35.26	$35.25	$35.30
Purchase #6	$80.89	11.660%	$90.3218	$90.32	$90.30	$90.30
Purchase #7	$84.83	10.554%	$93.783	$93.78	$93.80	$93.80
7 purchase totals =	$711.47		$771.8999	$771.89	$771.90	$772.00