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	$239.81	8.191%	$259.4528	$259.45	$259.45	$259.50
Purchase #2	$244.61	6.129%	$259.6021	$259.60	$259.60	$259.60
Purchase #3	$33.62	11.455%	$37.4712	$37.47	$37.45	$37.50
Purchase #4	$194.75	13.174%	$220.4064	$220.41	$220.40	$220.40
Purchase #5	$142.33	7.849%	$153.5015	$153.50	$153.50	$153.50
Purchase #6	$180.58	5.262%	$190.0821	$190.08	$190.10	$190.10
Purchase #7	$111.94	3.704%	$116.0863	$116.09	$116.10	$116.10
7 purchase totals =	$1,147.64		$1,236.6024	$1,236.60	$1,236.60	$1,236.70