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	$131.45	7.335%	$141.0919	$141.09	$141.10	$141.10
Purchase #2	$57.44	5.233%	$60.4458	$60.45	$60.45	$60.40
Purchase #3	$120.94	11.290%	$134.5941	$134.59	$134.60	$134.60
Purchase #4	$57.67	3.647%	$59.7732	$59.77	$59.75	$59.80
Purchase #5	$231.97	12.380%	$260.6879	$260.69	$260.70	$260.70
Purchase #6	$237.72	10.327%	$262.2693	$262.27	$262.25	$262.30
Purchase #7	$201.66	3.486%	$208.6899	$208.69	$208.70	$208.70
7 purchase totals =	$1,038.85		$1,127.5521	$1,127.55	$1,127.55	$1,127.60