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	$129.71	8.715%	$141.0142	$141.01	$141.00	$141.00
Purchase #2	$192.80	13.523%	$218.8723	$218.87	$218.85	$218.90
Purchase #3	$80.54	3.778%	$83.5828	$83.58	$83.60	$83.60
Purchase #4	$32.84	12.543%	$36.9591	$36.96	$36.95	$37.00
Purchase #5	$186.37	11.652%	$208.0858	$208.09	$208.10	$208.10
Purchase #6	$131.59	6.787%	$140.521	$140.52	$140.50	$140.50
Purchase #7	$35.75	10.116%	$39.3665	$39.37	$39.35	$39.40
7 purchase totals =	$789.60		$868.4017	$868.40	$868.35	$868.50