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	$10.67	6.210%	$11.3326	$11.33	$11.35	$11.30
Purchase #2	$49.92	3.789%	$51.8115	$51.81	$51.80	$51.80
Purchase #3	$12.53	5.194%	$13.1808	$13.18	$13.20	$13.20
Purchase #4	$190.67	5.325%	$200.8232	$200.82	$200.80	$200.80
Purchase #5	$151.34	7.667%	$162.9432	$162.94	$162.95	$162.90
Purchase #6	$132.56	7.523%	$142.5325	$142.53	$142.55	$142.50
Purchase #7	$94.66	10.868%	$104.9476	$104.95	$104.95	$104.90
7 purchase totals =	$642.35		$687.5714	$687.56	$687.60	$687.40