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	$101.31	10.509%	$111.9567	$111.96	$111.95	$112.00
Purchase #2	$20.70	7.709%	$22.2958	$22.30	$22.30	$22.30
Purchase #3	$223.95	10.245%	$246.8937	$246.89	$246.90	$246.90
Purchase #4	$194.55	5.621%	$205.4857	$205.49	$205.50	$205.50
Purchase #5	$200.25	4.151%	$208.5624	$208.56	$208.55	$208.60
Purchase #6	$32.39	4.789%	$33.9412	$33.94	$33.95	$33.90
Purchase #7	$27.68	13.139%	$31.3169	$31.32	$31.30	$31.30
7 purchase totals =	$800.83		$860.4524	$860.46	$860.45	$860.50