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	$209.92	9.711%	$230.3053	$230.31	$230.30	$230.30
Purchase #2	$13.54	3.337%	$13.9918	$13.99	$14.00	$14.00
Purchase #3	$19.35	13.264%	$21.9166	$21.92	$21.90	$21.90
Purchase #4	$172.71	8.339%	$187.1123	$187.11	$187.10	$187.10
Purchase #5	$63.31	9.573%	$69.3707	$69.37	$69.35	$69.40
Purchase #6	$11.98	13.452%	$13.5915	$13.59	$13.60	$13.60
Purchase #7	$118.82	10.613%	$131.4304	$131.43	$131.45	$131.40
7 purchase totals =	$609.63		$667.7186	$667.72	$667.70	$667.70