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	$9.45	12.369%	$10.6189	$10.62	$10.60	$10.60
Purchase #2	$57.33	13.391%	$65.0071	$65.01	$65.00	$65.00
Purchase #3	$115.49	6.827%	$123.3745	$123.37	$123.35	$123.40
Purchase #4	$180.56	3.348%	$186.6051	$186.61	$186.60	$186.60
Purchase #5	$109.60	8.131%	$118.5116	$118.51	$118.50	$118.50
Purchase #6	$153.84	4.317%	$160.4813	$160.48	$160.50	$160.50
Purchase #7	$195.97	11.179%	$217.8775	$217.88	$217.90	$217.90
7 purchase totals =	$822.24		$882.4760	$882.48	$882.45	$882.50