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	$67.39	3.262%	$69.5883	$69.59	$69.60	$69.60
Purchase #2	$220.67	7.871%	$238.0389	$238.04	$238.05	$238.00
Purchase #3	$43.28	10.149%	$47.6725	$47.67	$47.65	$47.70
Purchase #4	$82.89	9.371%	$90.6576	$90.66	$90.65	$90.70
Purchase #5	$7.85	8.573%	$8.523	$8.52	$8.50	$8.50
Purchase #6	$156.47	10.351%	$172.6662	$172.67	$172.65	$172.70
Purchase #7	$143.59	10.709%	$158.9671	$158.97	$158.95	$159.00
7 purchase totals =	$722.14		$786.1136	$786.12	$786.05	$786.20