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	$131.80	8.690%	$143.2534	$143.25	$143.25	$143.30
Purchase #2	$242.40	5.509%	$255.7538	$255.75	$255.75	$255.80
Purchase #3	$65.45	10.579%	$72.374	$72.37	$72.35	$72.40
Purchase #4	$13.76	8.751%	$14.9641	$14.96	$14.95	$15.00
Purchase #5	$175.51	8.462%	$190.3617	$190.36	$190.35	$190.40
Purchase #6	$90.53	8.786%	$98.484	$98.48	$98.50	$98.50
Purchase #7	$21.39	9.838%	$23.4943	$23.49	$23.50	$23.50
7 purchase totals =	$740.84		$798.6853	$798.66	$798.65	$798.90