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	$115.71	10.585%	$127.9579	$127.96	$127.95	$128.00
Purchase #2	$169.66	7.602%	$182.5576	$182.56	$182.55	$182.60
Purchase #3	$132.55	12.798%	$149.5137	$149.51	$149.50	$149.50
Purchase #4	$95.75	5.291%	$100.8161	$100.82	$100.80	$100.80
Purchase #5	$223.90	3.758%	$232.3142	$232.31	$232.30	$232.30
Purchase #6	$56.88	6.284%	$60.4543	$60.45	$60.45	$60.50
Purchase #7	$131.46	10.537%	$145.3119	$145.31	$145.30	$145.30
7 purchase totals =	$925.91		$998.9257	$998.92	$998.85	$999.00