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	$116.33	13.208%	$131.6949	$131.69	$131.70	$131.70
Purchase #2	$113.79	11.568%	$126.9532	$126.95	$126.95	$127.00
Purchase #3	$176.60	5.133%	$185.6649	$185.66	$185.65	$185.70
Purchase #4	$48.57	11.377%	$54.0958	$54.10	$54.10	$54.10
Purchase #5	$48.68	9.300%	$53.2072	$53.21	$53.20	$53.20
Purchase #6	$131.79	8.111%	$142.4795	$142.48	$142.50	$142.50
Purchase #7	$29.38	8.340%	$31.8303	$31.83	$31.85	$31.80
7 purchase totals =	$665.14		$725.9258	$725.92	$725.95	$726.00