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	$128.90	3.379%	$133.2555	$133.26	$133.25	$133.30
Purchase #2	$179.60	4.227%	$187.1917	$187.19	$187.20	$187.20
Purchase #3	$82.41	10.191%	$90.8084	$90.81	$90.80	$90.80
Purchase #4	$191.57	8.835%	$208.4952	$208.50	$208.50	$208.50
Purchase #5	$48.79	3.483%	$50.4894	$50.49	$50.50	$50.50
Purchase #6	$162.95	8.229%	$176.3592	$176.36	$176.35	$176.40
Purchase #7	$20.67	5.684%	$21.8449	$21.84	$21.85	$21.80
7 purchase totals =	$814.89		$868.4443	$868.45	$868.45	$868.50