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	$7.29	5.708%	$7.7061	$7.71	$7.70	$7.70
Purchase #2	$72.94	10.291%	$80.4463	$80.45	$80.45	$80.40
Purchase #3	$49.38	8.855%	$53.7526	$53.75	$53.75	$53.80
Purchase #4	$223.74	5.704%	$236.5021	$236.50	$236.50	$236.50
Purchase #5	$249.97	12.248%	$280.5863	$280.59	$280.60	$280.60
Purchase #6	$213.48	12.859%	$240.9314	$240.93	$240.95	$240.90
Purchase #7	$233.83	4.389%	$244.0928	$244.09	$244.10	$244.10
7 purchase totals =	$1,050.63		$1,144.0176	$1,144.02	$1,144.05	$1,144.00