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	$105.58	5.581%	$111.4724	$111.47	$111.45	$111.50
Purchase #2	$112.28	12.691%	$126.5295	$126.53	$126.55	$126.50
Purchase #3	$75.96	9.358%	$83.0683	$83.07	$83.05	$83.10
Purchase #4	$89.72	8.773%	$97.5911	$97.59	$97.60	$97.60
Purchase #5	$190.93	7.800%	$205.8225	$205.82	$205.80	$205.80
Purchase #6	$178.85	10.179%	$197.0551	$197.06	$197.05	$197.10
Purchase #7	$192.93	10.672%	$213.5195	$213.52	$213.50	$213.50
7 purchase totals =	$946.25		$1,035.0584	$1,035.06	$1,035.00	$1,035.10