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	$95.33	10.632%	$105.4655	$105.47	$105.45	$105.50
Purchase #2	$217.41	5.828%	$230.0807	$230.08	$230.10	$230.10
Purchase #3	$21.69	13.226%	$24.5587	$24.56	$24.55	$24.60
Purchase #4	$82.80	5.635%	$87.4658	$87.47	$87.45	$87.50
Purchase #5	$58.46	10.396%	$64.5375	$64.54	$64.55	$64.50
Purchase #6	$148.78	5.310%	$156.6802	$156.68	$156.70	$156.70
Purchase #7	$94.60	5.527%	$99.8285	$99.83	$99.85	$99.80
7 purchase totals =	$719.07		$768.6169	$768.63	$768.65	$768.70