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	$117.90	12.724%	$132.9016	$132.90	$132.90	$132.90
Purchase #2	$208.35	9.194%	$227.5057	$227.51	$227.50	$227.50
Purchase #3	$109.91	3.617%	$113.8854	$113.89	$113.90	$113.90
Purchase #4	$234.55	12.484%	$263.8312	$263.83	$263.85	$263.80
Purchase #5	$28.63	11.521%	$31.9285	$31.93	$31.95	$31.90
Purchase #6	$5.77	13.752%	$6.5635	$6.56	$6.55	$6.60
Purchase #7	$196.79	4.416%	$205.4802	$205.48	$205.50	$205.50
7 purchase totals =	$901.90		$982.0961	$982.10	$982.15	$982.10