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	$241.89	12.145%	$271.2675	$271.27	$271.25	$271.30
Purchase #2	$117.69	4.849%	$123.3968	$123.40	$123.40	$123.40
Purchase #3	$179.44	5.185%	$188.744	$188.74	$188.75	$188.70
Purchase #4	$105.25	5.705%	$111.2545	$111.25	$111.25	$111.30
Purchase #5	$153.64	8.675%	$166.9683	$166.97	$166.95	$167.00
Purchase #6	$109.38	6.832%	$116.8528	$116.85	$116.85	$116.90
Purchase #7	$218.34	8.447%	$236.7832	$236.78	$236.80	$236.80
7 purchase totals =	$1,125.63		$1,215.2671	$1,215.26	$1,215.25	$1,215.40