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	$95.41	10.724%	$105.6418	$105.64	$105.65	$105.60
Purchase #2	$143.37	10.554%	$158.5013	$158.50	$158.50	$158.50
Purchase #3	$65.96	3.781%	$68.4539	$68.45	$68.45	$68.50
Purchase #4	$36.48	10.509%	$40.3137	$40.31	$40.30	$40.30
Purchase #5	$53.32	7.778%	$57.4672	$57.47	$57.45	$57.50
Purchase #6	$167.37	13.706%	$190.3097	$190.31	$190.30	$190.30
Purchase #7	$28.70	8.848%	$31.2394	$31.24	$31.25	$31.20
7 purchase totals =	$590.61		$651.9270	$651.92	$651.90	$651.90