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	$126.39	10.338%	$139.4562	$139.46	$139.45	$139.50
Purchase #2	$189.84	12.243%	$213.0821	$213.08	$213.10	$213.10
Purchase #3	$184.53	6.574%	$196.661	$196.66	$196.65	$196.70
Purchase #4	$182.59	4.287%	$190.4176	$190.42	$190.40	$190.40
Purchase #5	$76.87	6.473%	$81.8458	$81.85	$81.85	$81.80
Purchase #6	$124.70	7.808%	$134.4366	$134.44	$134.45	$134.40
Purchase #7	$246.82	3.747%	$256.0683	$256.07	$256.05	$256.10
7 purchase totals =	$1,131.74		$1,211.9676	$1,211.98	$1,211.95	$1,212.00