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	$234.53	9.609%	$257.066	$257.07	$257.05	$257.10
Purchase #2	$207.98	3.622%	$215.513	$215.51	$215.50	$215.50
Purchase #3	$54.58	12.509%	$61.4074	$61.41	$61.40	$61.40
Purchase #4	$211.35	10.476%	$233.491	$233.49	$233.50	$233.50
Purchase #5	$118.45	4.297%	$123.5398	$123.54	$123.55	$123.50
Purchase #6	$249.96	12.156%	$280.3451	$280.35	$280.35	$280.30
Purchase #7	$151.26	8.866%	$164.6707	$164.67	$164.65	$164.70
7 purchase totals =	$1,228.11		$1,336.0330	$1,336.04	$1,336.00	$1,336.00