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	$150.50	10.479%	$166.2709	$166.27	$166.25	$166.30
Purchase #2	$79.69	3.763%	$82.6887	$82.69	$82.70	$82.70
Purchase #3	$164.74	7.274%	$176.7232	$176.72	$176.70	$176.70
Purchase #4	$226.96	12.396%	$255.094	$255.09	$255.10	$255.10
Purchase #5	$122.86	9.504%	$134.5366	$134.54	$134.55	$134.50
Purchase #6	$97.36	4.357%	$101.602	$101.60	$101.60	$101.60
Purchase #7	$122.87	3.469%	$127.1324	$127.13	$127.15	$127.10
7 purchase totals =	$964.98		$1,044.0478	$1,044.04	$1,044.05	$1,044.00