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	$108.78	13.565%	$123.536	$123.54	$123.55	$123.50
Purchase #2	$20.53	12.716%	$23.1406	$23.14	$23.15	$23.10
Purchase #3	$87.77	11.248%	$97.6424	$97.64	$97.65	$97.60
Purchase #4	$248.69	12.741%	$280.3756	$280.38	$280.40	$280.40
Purchase #5	$12.25	9.540%	$13.4187	$13.42	$13.40	$13.40
Purchase #6	$22.56	9.557%	$24.7161	$24.72	$24.70	$24.70
Purchase #7	$67.98	6.850%	$72.6366	$72.64	$72.65	$72.60
7 purchase totals =	$568.56		$635.4660	$635.48	$635.50	$635.30