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	$248.40	3.491%	$257.0716	$257.07	$257.05	$257.10
Purchase #2	$239.79	6.696%	$255.8463	$255.85	$255.85	$255.80
Purchase #3	$82.52	9.754%	$90.569	$90.57	$90.55	$90.60
Purchase #4	$81.38	13.379%	$92.2678	$92.27	$92.25	$92.30
Purchase #5	$197.95	3.805%	$205.482	$205.48	$205.50	$205.50
Purchase #6	$41.61	10.474%	$45.9682	$45.97	$45.95	$46.00
Purchase #7	$92.83	8.866%	$101.0603	$101.06	$101.05	$101.10
7 purchase totals =	$984.48		$1,048.2652	$1,048.27	$1,048.20	$1,048.40