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	$87.75	12.143%	$98.4055	$98.41	$98.40	$98.40
Purchase #2	$105.83	6.304%	$112.5015	$112.50	$112.50	$112.50
Purchase #3	$151.99	4.197%	$158.369	$158.37	$158.35	$158.40
Purchase #4	$115.85	10.243%	$127.7165	$127.72	$127.70	$127.70
Purchase #5	$249.58	6.788%	$266.5215	$266.52	$266.50	$266.50
Purchase #6	$246.63	6.419%	$262.4612	$262.46	$262.45	$262.50
Purchase #7	$85.69	8.367%	$92.8597	$92.86	$92.85	$92.90
7 purchase totals =	$1,043.32		$1,118.8349	$1,118.84	$1,118.75	$1,118.90