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	$115.33	10.509%	$127.45	$127.45	$127.45	$127.50
Purchase #2	$38.50	8.369%	$41.7221	$41.72	$41.70	$41.70
Purchase #3	$60.98	4.431%	$63.682	$63.68	$63.70	$63.70
Purchase #4	$133.92	9.259%	$146.3197	$146.32	$146.30	$146.30
Purchase #5	$84.67	7.403%	$90.9381	$90.94	$90.95	$90.90
Purchase #6	$34.73	7.604%	$37.3709	$37.37	$37.35	$37.40
Purchase #7	$237.93	7.525%	$255.8342	$255.83	$255.85	$255.80
7 purchase totals =	$706.06		$763.3170	$763.31	$763.30	$763.30