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	$182.50	3.806%	$189.446	$189.45	$189.45	$189.40
Purchase #2	$233.66	9.804%	$256.568	$256.57	$256.55	$256.60
Purchase #3	$189.39	10.177%	$208.6642	$208.66	$208.65	$208.70
Purchase #4	$50.48	8.720%	$54.8819	$54.88	$54.90	$54.90
Purchase #5	$142.49	8.566%	$154.6957	$154.70	$154.70	$154.70
Purchase #6	$78.52	3.801%	$81.5045	$81.50	$81.50	$81.50
Purchase #7	$194.67	7.620%	$209.5039	$209.50	$209.50	$209.50
7 purchase totals =	$1,071.71		$1,155.2642	$1,155.26	$1,155.25	$1,155.30