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	$87.76	5.455%	$92.5473	$92.55	$92.55	$92.50
Purchase #2	$247.80	13.240%	$280.6087	$280.61	$280.60	$280.60
Purchase #3	$148.94	12.167%	$167.0615	$167.06	$167.05	$167.10
Purchase #4	$172.64	10.206%	$190.2596	$190.26	$190.25	$190.30
Purchase #5	$181.75	4.554%	$190.0269	$190.03	$190.05	$190.00
Purchase #6	$112.77	4.643%	$118.0059	$118.01	$118.00	$118.00
Purchase #7	$6.72	8.142%	$7.2671	$7.27	$7.25	$7.30
7 purchase totals =	$958.38		$1,045.7770	$1,045.79	$1,045.75	$1,045.80