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	$210.37	8.451%	$228.1484	$228.15	$228.15	$228.10
Purchase #2	$117.92	11.545%	$131.5339	$131.53	$131.55	$131.50
Purchase #3	$10.70	11.807%	$11.9633	$11.96	$11.95	$12.00
Purchase #4	$73.35	4.792%	$76.8649	$76.86	$76.85	$76.90
Purchase #5	$12.82	11.360%	$14.2764	$14.28	$14.30	$14.30
Purchase #6	$29.92	6.766%	$31.9444	$31.94	$31.95	$31.90
Purchase #7	$194.96	11.596%	$217.5676	$217.57	$217.55	$217.60
7 purchase totals =	$650.04		$712.2989	$712.29	$712.30	$712.30