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	$114.88	9.320%	$125.5868	$125.59	$125.60	$125.60
Purchase #2	$17.89	13.493%	$20.3039	$20.30	$20.30	$20.30
Purchase #3	$97.77	4.757%	$102.4209	$102.42	$102.40	$102.40
Purchase #4	$54.29	9.114%	$59.238	$59.24	$59.25	$59.20
Purchase #5	$102.26	5.691%	$108.0796	$108.08	$108.10	$108.10
Purchase #6	$47.78	7.139%	$51.191	$51.19	$51.20	$51.20
Purchase #7	$171.90	4.717%	$180.0085	$180.01	$180.00	$180.00
7 purchase totals =	$606.77		$646.8287	$646.83	$646.85	$646.80