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	$246.38	5.860%	$260.8179	$260.82	$260.80	$260.80
Purchase #2	$38.59	13.649%	$43.8571	$43.86	$43.85	$43.90
Purchase #3	$157.94	6.517%	$168.2329	$168.23	$168.25	$168.20
Purchase #4	$42.50	13.149%	$48.0883	$48.09	$48.10	$48.10
Purchase #5	$238.67	5.141%	$250.94	$250.94	$250.95	$250.90
Purchase #6	$142.66	6.262%	$151.5934	$151.59	$151.60	$151.60
Purchase #7	$13.39	4.544%	$13.9984	$14.00	$14.00	$14.00
7 purchase totals =	$880.13		$937.5280	$937.53	$937.55	$937.50