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	$145.28	7.735%	$156.5174	$156.52	$156.50	$156.50
Purchase #2	$67.89	10.297%	$74.8806	$74.88	$74.90	$74.90
Purchase #3	$50.87	7.284%	$54.5754	$54.58	$54.60	$54.60
Purchase #4	$113.38	6.509%	$120.7599	$120.76	$120.75	$120.80
Purchase #5	$11.56	8.188%	$12.5065	$12.51	$12.50	$12.50
Purchase #6	$110.47	11.337%	$122.994	$122.99	$123.00	$123.00
Purchase #7	$118.39	11.303%	$131.7716	$131.77	$131.75	$131.80
7 purchase totals =	$617.84		$674.0054	$674.01	$674.00	$674.10