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	$212.25	11.602%	$236.8752	$236.88	$236.90	$236.90
Purchase #2	$107.70	4.356%	$112.3914	$112.39	$112.40	$112.40
Purchase #3	$190.72	4.690%	$199.6648	$199.66	$199.65	$199.70
Purchase #4	$10.39	13.870%	$11.8311	$11.83	$11.85	$11.80
Purchase #5	$116.27	6.556%	$123.8927	$123.89	$123.90	$123.90
Purchase #6	$204.33	5.231%	$215.0185	$215.02	$215.00	$215.00
Purchase #7	$59.40	12.632%	$66.9034	$66.90	$66.90	$66.90
7 purchase totals =	$901.06		$966.5771	$966.57	$966.60	$966.60