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	$112.49	5.758%	$118.9672	$118.97	$118.95	$119.00
Purchase #2	$50.77	3.823%	$52.7109	$52.71	$52.70	$52.70
Purchase #3	$158.50	9.526%	$173.5987	$173.60	$173.60	$173.60
Purchase #4	$78.45	10.183%	$86.4386	$86.44	$86.45	$86.40
Purchase #5	$198.69	7.242%	$213.0791	$213.08	$213.10	$213.10
Purchase #6	$81.80	9.466%	$89.5432	$89.54	$89.55	$89.50
Purchase #7	$15.75	13.693%	$17.9066	$17.91	$17.90	$17.90
7 purchase totals =	$696.45		$752.2443	$752.25	$752.25	$752.20