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	$102.67	10.745%	$113.7019	$113.70	$113.70	$113.70
Purchase #2	$127.43	12.607%	$143.4951	$143.50	$143.50	$143.50
Purchase #3	$163.69	5.149%	$172.1184	$172.12	$172.10	$172.10
Purchase #4	$68.71	7.450%	$73.8289	$73.83	$73.85	$73.80
Purchase #5	$133.44	8.152%	$144.318	$144.32	$144.30	$144.30
Purchase #6	$247.51	13.532%	$281.0031	$281.00	$281.00	$281.00
Purchase #7	$148.62	3.232%	$153.4234	$153.42	$153.40	$153.40
7 purchase totals =	$992.07		$1,081.8888	$1,081.89	$1,081.85	$1,081.80