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	$143.25	9.166%	$156.3803	$156.38	$156.40	$156.40
Purchase #2	$59.86	4.549%	$62.583	$62.58	$62.60	$62.60
Purchase #3	$82.32	9.863%	$90.4392	$90.44	$90.45	$90.40
Purchase #4	$123.28	11.597%	$137.5768	$137.58	$137.60	$137.60
Purchase #5	$120.95	9.642%	$132.612	$132.61	$132.60	$132.60
Purchase #6	$217.66	3.873%	$226.09	$226.09	$226.10	$226.10
Purchase #7	$194.36	8.526%	$210.9311	$210.93	$210.95	$210.90
7 purchase totals =	$941.68		$1,016.6124	$1,016.61	$1,016.70	$1,016.60