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	$97.80	10.809%	$108.3712	$108.37	$108.35	$108.40
Purchase #2	$63.79	4.400%	$66.5968	$66.60	$66.60	$66.60
Purchase #3	$32.31	7.529%	$34.7426	$34.74	$34.75	$34.70
Purchase #4	$85.88	5.289%	$90.4222	$90.42	$90.40	$90.40
Purchase #5	$145.61	12.680%	$164.0733	$164.07	$164.05	$164.10
Purchase #6	$57.94	9.283%	$63.3186	$63.32	$63.30	$63.30
Purchase #7	$78.27	13.552%	$88.8772	$88.88	$88.90	$88.90
7 purchase totals =	$561.60		$616.4019	$616.40	$616.35	$616.40