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	$173.89	12.487%	$195.6036	$195.60	$195.60	$195.60
Purchase #2	$157.48	4.507%	$164.5776	$164.58	$164.60	$164.60
Purchase #3	$238.70	6.828%	$254.9984	$255.00	$255.00	$255.00
Purchase #4	$139.68	13.170%	$158.0759	$158.08	$158.10	$158.10
Purchase #5	$95.53	8.168%	$103.3329	$103.33	$103.35	$103.30
Purchase #6	$114.35	4.384%	$119.3631	$119.36	$119.35	$119.40
Purchase #7	$11.51	8.537%	$12.4926	$12.49	$12.50	$12.50
7 purchase totals =	$931.14		$1,008.4441	$1,008.44	$1,008.50	$1,008.50