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	$104.72	6.504%	$111.531	$111.53	$111.55	$111.50
Purchase #2	$142.50	11.759%	$159.2566	$159.26	$159.25	$159.30
Purchase #3	$113.72	5.482%	$119.9541	$119.95	$119.95	$120.00
Purchase #4	$192.83	8.203%	$208.6478	$208.65	$208.65	$208.60
Purchase #5	$181.51	4.477%	$189.6362	$189.64	$189.65	$189.60
Purchase #6	$50.59	6.612%	$53.935	$53.94	$53.95	$53.90
Purchase #7	$133.90	4.328%	$139.6952	$139.70	$139.70	$139.70
7 purchase totals =	$919.77		$982.6559	$982.67	$982.70	$982.60