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	$116.64	12.326%	$131.017	$131.02	$131.00	$131.00
Purchase #2	$117.43	13.851%	$133.6952	$133.70	$133.70	$133.70
Purchase #3	$246.90	3.829%	$256.3538	$256.35	$256.35	$256.40
Purchase #4	$180.43	13.871%	$205.4574	$205.46	$205.45	$205.50
Purchase #5	$162.46	13.537%	$184.4522	$184.45	$184.45	$184.50
Purchase #6	$17.95	13.506%	$20.3743	$20.37	$20.35	$20.40
Purchase #7	$189.55	10.196%	$208.8765	$208.88	$208.90	$208.90
7 purchase totals =	$1,031.36		$1,140.2264	$1,140.23	$1,140.20	$1,140.40