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	$69.56	3.856%	$72.2422	$72.24	$72.25	$72.20
Purchase #2	$98.57	11.229%	$109.6384	$109.64	$109.65	$109.60
Purchase #3	$227.32	13.275%	$257.4967	$257.50	$257.50	$257.50
Purchase #4	$144.70	11.325%	$161.0873	$161.09	$161.10	$161.10
Purchase #5	$119.34	6.291%	$126.8477	$126.85	$126.85	$126.80
Purchase #6	$142.69	11.328%	$158.8539	$158.85	$158.85	$158.90
Purchase #7	$73.46	4.276%	$76.6011	$76.60	$76.60	$76.60
7 purchase totals =	$875.64		$962.7673	$962.77	$962.80	$962.70