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	$83.96	13.819%	$95.5624	$95.56	$95.55	$95.60
Purchase #2	$64.59	11.755%	$72.1826	$72.18	$72.20	$72.20
Purchase #3	$118.86	13.521%	$134.9311	$134.93	$134.95	$134.90
Purchase #4	$33.54	3.582%	$34.7414	$34.74	$34.75	$34.70
Purchase #5	$131.74	8.186%	$142.5242	$142.52	$142.50	$142.50
Purchase #6	$244.90	4.129%	$255.0119	$255.01	$255.00	$255.00
Purchase #7	$108.94	7.115%	$116.6911	$116.69	$116.70	$116.70
7 purchase totals =	$786.53		$851.6447	$851.63	$851.65	$851.60