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	$51.61	13.404%	$58.5278	$58.53	$58.55	$58.50
Purchase #2	$97.29	4.763%	$101.9239	$101.92	$101.90	$101.90
Purchase #3	$194.52	12.474%	$218.7844	$218.78	$218.80	$218.80
Purchase #4	$38.70	7.509%	$41.606	$41.61	$41.60	$41.60
Purchase #5	$157.34	9.305%	$171.9805	$171.98	$172.00	$172.00
Purchase #6	$209.69	8.695%	$227.9225	$227.92	$227.90	$227.90
Purchase #7	$111.90	13.715%	$127.2471	$127.25	$127.25	$127.20
7 purchase totals =	$861.05		$947.9922	$947.99	$948.00	$947.90