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	$236.84	8.538%	$257.0614	$257.06	$257.05	$257.10
Purchase #2	$52.95	11.748%	$59.1706	$59.17	$59.15	$59.20
Purchase #3	$249.48	12.509%	$280.6875	$280.69	$280.70	$280.70
Purchase #4	$87.35	3.803%	$90.6719	$90.67	$90.65	$90.70
Purchase #5	$186.75	5.298%	$196.644	$196.64	$196.65	$196.60
Purchase #6	$35.93	4.798%	$37.6539	$37.65	$37.65	$37.70
Purchase #7	$55.32	7.163%	$59.2826	$59.28	$59.30	$59.30
7 purchase totals =	$904.62		$981.1719	$981.16	$981.15	$981.30