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	$50.48	6.425%	$53.7233	$53.72	$53.70	$53.70
Purchase #2	$119.84	10.553%	$132.4867	$132.49	$132.50	$132.50
Purchase #3	$237.56	7.379%	$255.0896	$255.09	$255.10	$255.10
Purchase #4	$246.87	13.618%	$280.4888	$280.49	$280.50	$280.50
Purchase #5	$60.69	13.195%	$68.698	$68.70	$68.70	$68.70
Purchase #6	$231.85	13.359%	$262.8228	$262.82	$262.80	$262.80
Purchase #7	$97.54	5.502%	$102.9067	$102.91	$102.90	$102.90
7 purchase totals =	$1,044.83		$1,156.2159	$1,156.22	$1,156.20	$1,156.20