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	$56.94	6.826%	$60.8267	$60.83	$60.85	$60.80
Purchase #2	$7.39	13.293%	$8.3724	$8.37	$8.35	$8.40
Purchase #3	$238.89	12.564%	$268.9041	$268.90	$268.90	$268.90
Purchase #4	$58.61	4.834%	$61.4432	$61.44	$61.45	$61.40
Purchase #5	$248.55	3.660%	$257.6469	$257.65	$257.65	$257.60
Purchase #6	$122.41	4.149%	$127.4888	$127.49	$127.50	$127.50
Purchase #7	$10.77	10.422%	$11.8924	$11.89	$11.90	$11.90
7 purchase totals =	$743.56		$796.5745	$796.57	$796.60	$796.50