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	$114.52	11.393%	$127.5673	$127.57	$127.55	$127.60
Purchase #2	$108.97	8.826%	$118.5877	$118.59	$118.60	$118.60
Purchase #3	$127.79	9.155%	$139.4892	$139.49	$139.50	$139.50
Purchase #4	$192.96	13.244%	$218.5156	$218.52	$218.50	$218.50
Purchase #5	$145.97	9.472%	$159.7963	$159.80	$159.80	$159.80
Purchase #6	$93.46	12.870%	$105.4883	$105.49	$105.50	$105.50
Purchase #7	$58.85	7.497%	$63.262	$63.26	$63.25	$63.30
7 purchase totals =	$842.52		$932.7064	$932.72	$932.70	$932.80