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	$231.59	3.455%	$239.5914	$239.59	$239.60	$239.60
Purchase #2	$168.97	13.526%	$191.8249	$191.82	$191.80	$191.80
Purchase #3	$85.35	8.833%	$92.889	$92.89	$92.90	$92.90
Purchase #4	$102.73	8.509%	$111.4713	$111.47	$111.45	$111.50
Purchase #5	$82.57	11.477%	$92.0466	$92.05	$92.05	$92.00
Purchase #6	$176.89	7.795%	$190.6786	$190.68	$190.70	$190.70
Purchase #7	$77.48	5.218%	$81.5229	$81.52	$81.50	$81.50
7 purchase totals =	$925.58		$1,000.0247	$1,000.02	$1,000.00	$1,000.00