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	$205.32	8.302%	$222.3657	$222.37	$222.35	$222.40
Purchase #2	$102.49	10.763%	$113.521	$113.52	$113.50	$113.50
Purchase #3	$116.46	12.478%	$130.9919	$130.99	$131.00	$131.00
Purchase #4	$187.69	13.782%	$213.5574	$213.56	$213.55	$213.60
Purchase #5	$14.59	4.589%	$15.2595	$15.26	$15.25	$15.30
Purchase #6	$74.78	5.360%	$78.7882	$78.79	$78.80	$78.80
Purchase #7	$166.84	13.863%	$189.969	$189.97	$189.95	$190.00
7 purchase totals =	$868.17		$964.4527	$964.46	$964.40	$964.60