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	$216.46	12.856%	$244.2881	$244.29	$244.30	$244.30
Purchase #2	$234.94	8.788%	$255.5865	$255.59	$255.60	$255.60
Purchase #3	$70.58	11.236%	$78.5104	$78.51	$78.50	$78.50
Purchase #4	$148.58	6.730%	$158.5794	$158.58	$158.60	$158.60
Purchase #5	$228.58	3.537%	$236.6649	$236.66	$236.65	$236.70
Purchase #6	$249.34	3.318%	$257.6131	$257.61	$257.60	$257.60
Purchase #7	$28.83	9.321%	$31.5172	$31.52	$31.50	$31.50
7 purchase totals =	$1,177.31		$1,262.7596	$1,262.76	$1,262.75	$1,262.80