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	$143.71	10.564%	$158.8915	$158.89	$158.90	$158.90
Purchase #2	$72.78	10.580%	$80.4801	$80.48	$80.50	$80.50
Purchase #3	$116.45	10.419%	$128.5829	$128.58	$128.60	$128.60
Purchase #4	$213.76	10.209%	$235.5828	$235.58	$235.60	$235.60
Purchase #5	$202.60	3.752%	$210.2016	$210.20	$210.20	$210.20
Purchase #6	$108.26	5.704%	$114.4352	$114.44	$114.45	$114.40
Purchase #7	$82.91	9.465%	$90.7574	$90.76	$90.75	$90.80
7 purchase totals =	$940.47		$1,018.9315	$1,018.93	$1,019.00	$1,019.00