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	$118.34	11.300%	$131.7124	$131.71	$131.70	$131.70
Purchase #2	$179.60	5.458%	$189.4026	$189.40	$189.40	$189.40
Purchase #3	$112.26	13.810%	$127.7631	$127.76	$127.75	$127.80
Purchase #4	$38.90	4.679%	$40.7201	$40.72	$40.70	$40.70
Purchase #5	$205.25	10.605%	$227.0168	$227.02	$227.00	$227.00
Purchase #6	$57.59	8.429%	$62.4443	$62.44	$62.45	$62.40
Purchase #7	$165.55	7.209%	$177.4845	$177.48	$177.50	$177.50
7 purchase totals =	$877.49		$956.5438	$956.53	$956.50	$956.50