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	$12.51	13.709%	$14.225	$14.23	$14.25	$14.20
Purchase #2	$38.64	3.113%	$39.8429	$39.84	$39.85	$39.80
Purchase #3	$131.81	4.143%	$137.2709	$137.27	$137.25	$137.30
Purchase #4	$105.66	10.437%	$116.6877	$116.69	$116.70	$116.70
Purchase #5	$190.51	10.363%	$210.2526	$210.25	$210.25	$210.30
Purchase #6	$246.53	10.120%	$271.4788	$271.48	$271.50	$271.50
Purchase #7	$74.90	4.252%	$78.0847	$78.08	$78.10	$78.10
7 purchase totals =	$800.56		$867.8426	$867.84	$867.90	$867.90