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	$94.36	5.218%	$99.2837	$99.28	$99.30	$99.30
Purchase #2	$58.58	6.795%	$62.5605	$62.56	$62.55	$62.60
Purchase #3	$146.32	7.493%	$157.2838	$157.28	$157.30	$157.30
Purchase #4	$76.59	8.725%	$83.2725	$83.27	$83.25	$83.30
Purchase #5	$42.77	7.559%	$46.003	$46.00	$46.00	$46.00
Purchase #6	$7.96	4.602%	$8.3263	$8.33	$8.35	$8.30
Purchase #7	$155.83	8.613%	$169.2516	$169.25	$169.25	$169.30
7 purchase totals =	$582.41		$625.9814	$625.97	$626.00	$626.10