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	$87.88	10.253%	$96.8903	$96.89	$96.90	$96.90
Purchase #2	$164.56	9.406%	$180.0385	$180.04	$180.05	$180.00
Purchase #3	$66.92	7.779%	$72.1257	$72.13	$72.15	$72.10
Purchase #4	$105.85	11.143%	$117.6449	$117.64	$117.65	$117.60
Purchase #5	$97.43	10.455%	$107.6163	$107.62	$107.60	$107.60
Purchase #6	$158.67	8.845%	$172.7044	$172.70	$172.70	$172.70
Purchase #7	$249.51	5.172%	$262.4147	$262.41	$262.40	$262.40
7 purchase totals =	$930.82		$1,009.4348	$1,009.43	$1,009.45	$1,009.30