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	$78.44	9.136%	$85.6063	$85.61	$85.60	$85.60
Purchase #2	$141.87	7.684%	$152.7713	$152.77	$152.75	$152.80
Purchase #3	$179.80	4.456%	$187.8119	$187.81	$187.80	$187.80
Purchase #4	$38.45	6.392%	$40.9077	$40.91	$40.90	$40.90
Purchase #5	$218.68	3.642%	$226.6443	$226.64	$226.65	$226.60
Purchase #6	$168.51	4.477%	$176.0542	$176.05	$176.05	$176.10
Purchase #7	$80.48	12.776%	$90.7621	$90.76	$90.75	$90.80
7 purchase totals =	$906.23		$960.5578	$960.55	$960.50	$960.60