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	$126.81	10.807%	$140.5144	$140.51	$140.50	$140.50
Purchase #2	$126.59	8.671%	$137.5666	$137.57	$137.55	$137.60
Purchase #3	$241.87	5.808%	$255.9178	$255.92	$255.90	$255.90
Purchase #4	$19.38	8.360%	$21.0002	$21.00	$21.00	$21.00
Purchase #5	$72.44	11.401%	$80.6989	$80.70	$80.70	$80.70
Purchase #6	$157.69	6.871%	$168.5249	$168.52	$168.50	$168.50
Purchase #7	$144.90	10.102%	$159.5378	$159.54	$159.55	$159.50
7 purchase totals =	$889.68		$963.7606	$963.76	$963.70	$963.70