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	$106.79	5.308%	$112.4584	$112.46	$112.45	$112.50
Purchase #2	$20.91	4.367%	$21.8231	$21.82	$21.80	$21.80
Purchase #3	$228.85	8.179%	$247.5676	$247.57	$247.55	$247.60
Purchase #4	$100.50	3.392%	$103.909	$103.91	$103.90	$103.90
Purchase #5	$57.67	10.136%	$63.5154	$63.52	$63.50	$63.50
Purchase #6	$27.97	12.795%	$31.5488	$31.55	$31.55	$31.50
Purchase #7	$117.76	3.119%	$121.4329	$121.43	$121.45	$121.40
7 purchase totals =	$660.45		$702.2552	$702.26	$702.20	$702.20