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	$227.63	12.623%	$256.3637	$256.36	$256.35	$256.40
Purchase #2	$69.29	6.554%	$73.8313	$73.83	$73.85	$73.80
Purchase #3	$78.82	9.708%	$86.4718	$86.47	$86.45	$86.50
Purchase #4	$162.83	10.476%	$179.8881	$179.89	$179.90	$179.90
Purchase #5	$121.73	8.518%	$132.099	$132.10	$132.10	$132.10
Purchase #6	$71.25	6.792%	$76.0893	$76.09	$76.10	$76.10
Purchase #7	$205.68	9.522%	$225.2648	$225.26	$225.25	$225.30
7 purchase totals =	$937.23		$1,030.0080	$1,030.00	$1,030.00	$1,030.10