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	$105.32	13.509%	$119.5477	$119.55	$119.55	$119.50
Purchase #2	$140.41	10.615%	$155.3145	$155.31	$155.30	$155.30
Purchase #3	$51.70	10.127%	$56.9357	$56.94	$56.95	$56.90
Purchase #4	$188.71	10.210%	$207.9773	$207.98	$208.00	$208.00
Purchase #5	$69.93	12.198%	$78.4601	$78.46	$78.45	$78.50
Purchase #6	$18.56	12.751%	$20.9266	$20.93	$20.95	$20.90
Purchase #7	$119.90	11.208%	$133.3384	$133.34	$133.35	$133.30
7 purchase totals =	$694.53		$772.5003	$772.51	$772.55	$772.40