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	$53.73	10.705%	$59.4818	$59.48	$59.50	$59.50
Purchase #2	$28.85	9.839%	$31.6886	$31.69	$31.70	$31.70
Purchase #3	$153.99	12.730%	$173.5929	$173.59	$173.60	$173.60
Purchase #4	$35.45	8.264%	$38.3796	$38.38	$38.40	$38.40
Purchase #5	$101.75	11.436%	$113.3861	$113.39	$113.40	$113.40
Purchase #6	$92.50	12.290%	$103.8683	$103.87	$103.85	$103.90
Purchase #7	$156.35	13.720%	$177.8012	$177.80	$177.80	$177.80
7 purchase totals =	$622.62		$698.1985	$698.20	$698.25	$698.30