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	$139.76	13.216%	$158.2307	$158.23	$158.25	$158.20
Purchase #2	$82.44	9.791%	$90.5117	$90.51	$90.50	$90.50
Purchase #3	$84.67	12.735%	$95.4527	$95.45	$95.45	$95.50
Purchase #4	$177.94	10.734%	$197.0401	$197.04	$197.05	$197.00
Purchase #5	$132.70	8.511%	$143.9941	$143.99	$144.00	$144.00
Purchase #6	$111.39	11.232%	$123.9013	$123.90	$123.90	$123.90
Purchase #7	$146.86	4.483%	$153.4437	$153.44	$153.45	$153.40
7 purchase totals =	$875.76		$962.5743	$962.56	$962.60	$962.50