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	$143.29	10.794%	$158.7567	$158.76	$158.75	$158.80
Purchase #2	$156.83	3.861%	$162.8852	$162.89	$162.90	$162.90
Purchase #3	$241.80	9.257%	$264.1834	$264.18	$264.20	$264.20
Purchase #4	$133.28	4.487%	$139.2603	$139.26	$139.25	$139.30
Purchase #5	$108.65	4.485%	$113.523	$113.52	$113.50	$113.50
Purchase #6	$234.25	9.697%	$256.9652	$256.97	$256.95	$257.00
Purchase #7	$226.79	10.271%	$250.0836	$250.08	$250.10	$250.10
7 purchase totals =	$1,244.89		$1,345.6574	$1,345.66	$1,345.65	$1,345.80