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	$178.64	11.124%	$198.5119	$198.51	$198.50	$198.50
Purchase #2	$100.30	10.865%	$111.1976	$111.20	$111.20	$111.20
Purchase #3	$179.36	8.509%	$194.6217	$194.62	$194.60	$194.60
Purchase #4	$64.94	11.254%	$72.2483	$72.25	$72.25	$72.20
Purchase #5	$188.36	12.215%	$211.3682	$211.37	$211.35	$211.40
Purchase #6	$116.81	13.298%	$132.3434	$132.34	$132.35	$132.30
Purchase #7	$60.96	4.479%	$63.6904	$63.69	$63.70	$63.70
7 purchase totals =	$889.37		$983.9815	$983.98	$983.95	$983.90