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	$119.90	9.730%	$131.5663	$131.57	$131.55	$131.60
Purchase #2	$146.39	8.524%	$158.8683	$158.87	$158.85	$158.90
Purchase #3	$143.62	9.619%	$157.4348	$157.43	$157.45	$157.40
Purchase #4	$132.45	7.497%	$142.3798	$142.38	$142.40	$142.40
Purchase #5	$123.52	13.211%	$139.8382	$139.84	$139.85	$139.80
Purchase #6	$94.66	8.303%	$102.5196	$102.52	$102.50	$102.50
Purchase #7	$228.74	3.780%	$237.3864	$237.39	$237.40	$237.40
7 purchase totals =	$989.28		$1,069.9934	$1,070.00	$1,070.00	$1,070.00