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	$205.67	8.686%	$223.5345	$223.53	$223.55	$223.50
Purchase #2	$100.98	4.667%	$105.6927	$105.69	$105.70	$105.70
Purchase #3	$78.62	6.656%	$83.8529	$83.85	$83.85	$83.90
Purchase #4	$125.78	5.655%	$132.8929	$132.89	$132.90	$132.90
Purchase #5	$19.33	11.256%	$21.5058	$21.51	$21.50	$21.50
Purchase #6	$221.31	9.262%	$241.8077	$241.81	$241.80	$241.80
Purchase #7	$167.83	5.166%	$176.5001	$176.50	$176.50	$176.50
7 purchase totals =	$919.52		$985.7866	$985.78	$985.80	$985.80