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	$81.62	4.836%	$85.5671	$85.57	$85.55	$85.60
Purchase #2	$38.75	4.660%	$40.5558	$40.56	$40.55	$40.60
Purchase #3	$50.40	5.549%	$53.1967	$53.20	$53.20	$53.20
Purchase #4	$239.99	6.615%	$255.8653	$255.87	$255.85	$255.90
Purchase #5	$141.38	9.208%	$154.3983	$154.40	$154.40	$154.40
Purchase #6	$140.43	11.495%	$156.5724	$156.57	$156.55	$156.60
Purchase #7	$216.99	9.429%	$237.45	$237.45	$237.45	$237.50
7 purchase totals =	$909.56		$983.6056	$983.62	$983.55	$983.80