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	$86.82	4.735%	$90.9309	$90.93	$90.95	$90.90
Purchase #2	$241.96	5.680%	$255.7033	$255.70	$255.70	$255.70
Purchase #3	$119.92	9.794%	$131.665	$131.67	$131.65	$131.70
Purchase #4	$155.59	8.576%	$168.9334	$168.93	$168.95	$168.90
Purchase #5	$31.40	9.782%	$34.4715	$34.47	$34.45	$34.50
Purchase #6	$70.85	13.622%	$80.5012	$80.50	$80.50	$80.50
Purchase #7	$67.72	3.167%	$69.8647	$69.86	$69.85	$69.90
7 purchase totals =	$774.26		$832.0700	$832.06	$832.05	$832.10