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	$121.68	3.117%	$125.4728	$125.47	$125.45	$125.50
Purchase #2	$228.97	13.671%	$260.2725	$260.27	$260.25	$260.30
Purchase #3	$46.48	7.296%	$49.8712	$49.87	$49.85	$49.90
Purchase #4	$247.84	13.312%	$280.8325	$280.83	$280.85	$280.80
Purchase #5	$145.39	9.295%	$158.904	$158.90	$158.90	$158.90
Purchase #6	$56.75	10.654%	$62.7961	$62.80	$62.80	$62.80
Purchase #7	$82.48	9.734%	$90.5086	$90.51	$90.50	$90.50
7 purchase totals =	$929.59		$1,028.6577	$1,028.65	$1,028.60	$1,028.70