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	$150.71	11.840%	$168.5541	$168.55	$168.55	$168.60
Purchase #2	$44.70	7.678%	$48.1321	$48.13	$48.15	$48.10
Purchase #3	$134.74	4.483%	$140.7804	$140.78	$140.80	$140.80
Purchase #4	$119.55	10.652%	$132.2845	$132.28	$132.30	$132.30
Purchase #5	$55.31	11.131%	$61.4666	$61.47	$61.45	$61.50
Purchase #6	$162.63	12.773%	$183.4027	$183.40	$183.40	$183.40
Purchase #7	$19.85	10.136%	$21.862	$21.86	$21.85	$21.90
7 purchase totals =	$687.49		$756.4824	$756.47	$756.50	$756.60