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	$13.44	7.382%	$14.4321	$14.43	$14.45	$14.40
Purchase #2	$84.56	11.463%	$94.2531	$94.25	$94.25	$94.30
Purchase #3	$71.80	7.158%	$76.9394	$76.94	$76.95	$76.90
Purchase #4	$76.74	7.376%	$82.4003	$82.40	$82.40	$82.40
Purchase #5	$150.80	5.124%	$158.527	$158.53	$158.55	$158.50
Purchase #6	$102.73	3.422%	$106.2454	$106.25	$106.25	$106.20
Purchase #7	$116.85	13.465%	$132.5839	$132.58	$132.60	$132.60
7 purchase totals =	$616.92		$665.3812	$665.38	$665.45	$665.30