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	$74.70	10.456%	$82.5106	$82.51	$82.50	$82.50
Purchase #2	$31.31	11.358%	$34.8662	$34.87	$34.85	$34.90
Purchase #3	$190.32	12.254%	$213.6418	$213.64	$213.65	$213.60
Purchase #4	$208.67	3.213%	$215.3746	$215.37	$215.35	$215.40
Purchase #5	$127.61	11.803%	$142.6718	$142.67	$142.65	$142.70
Purchase #6	$117.96	4.727%	$123.536	$123.54	$123.55	$123.50
Purchase #7	$166.83	5.509%	$176.0207	$176.02	$176.00	$176.00
7 purchase totals =	$917.40		$988.6217	$988.62	$988.55	$988.60