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	$161.44	13.117%	$182.6161	$182.62	$182.60	$182.60
Purchase #2	$144.45	3.395%	$149.3541	$149.35	$149.35	$149.40
Purchase #3	$131.88	11.165%	$146.6044	$146.60	$146.60	$146.60
Purchase #4	$129.37	8.785%	$140.7352	$140.74	$140.75	$140.70
Purchase #5	$150.68	9.356%	$164.7776	$164.78	$164.80	$164.80
Purchase #6	$132.37	5.244%	$139.3115	$139.31	$139.30	$139.30
Purchase #7	$154.50	5.235%	$162.5881	$162.59	$162.60	$162.60
7 purchase totals =	$1,004.69		$1,085.9870	$1,085.99	$1,086.00	$1,086.00