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	$126.27	5.585%	$133.3222	$133.32	$133.30	$133.30
Purchase #2	$65.82	10.373%	$72.6475	$72.65	$72.65	$72.60
Purchase #3	$38.66	5.638%	$40.8397	$40.84	$40.85	$40.80
Purchase #4	$140.25	7.573%	$150.8711	$150.87	$150.85	$150.90
Purchase #5	$186.42	3.288%	$192.5495	$192.55	$192.55	$192.50
Purchase #6	$78.42	7.595%	$84.376	$84.38	$84.40	$84.40
Purchase #7	$11.59	12.493%	$13.0379	$13.04	$13.05	$13.00
7 purchase totals =	$647.43		$687.6439	$687.65	$687.65	$687.50