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	$141.94	13.304%	$160.8237	$160.82	$160.80	$160.80
Purchase #2	$112.64	12.757%	$127.0095	$127.01	$127.00	$127.00
Purchase #3	$233.54	12.103%	$261.8053	$261.81	$261.80	$261.80
Purchase #4	$118.89	3.854%	$123.472	$123.47	$123.45	$123.50
Purchase #5	$210.44	3.472%	$217.7465	$217.75	$217.75	$217.70
Purchase #6	$38.44	12.535%	$43.2585	$43.26	$43.25	$43.30
Purchase #7	$140.66	8.856%	$153.1168	$153.12	$153.10	$153.10
7 purchase totals =	$996.55		$1,087.2323	$1,087.24	$1,087.15	$1,087.20