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	$244.35	10.823%	$270.796	$270.80	$270.80	$270.80
Purchase #2	$122.49	8.510%	$132.9139	$132.91	$132.90	$132.90
Purchase #3	$83.91	7.567%	$90.2595	$90.26	$90.25	$90.30
Purchase #4	$56.44	12.442%	$63.4623	$63.46	$63.45	$63.50
Purchase #5	$81.87	4.568%	$85.6098	$85.61	$85.60	$85.60
Purchase #6	$230.46	11.382%	$256.691	$256.69	$256.70	$256.70
Purchase #7	$51.39	7.618%	$55.3049	$55.30	$55.30	$55.30
7 purchase totals =	$870.91		$955.0374	$955.03	$955.00	$955.10