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	$121.87	8.803%	$132.5982	$132.60	$132.60	$132.60
Purchase #2	$234.26	8.438%	$254.0269	$254.03	$254.05	$254.00
Purchase #3	$47.87	10.774%	$53.0275	$53.03	$53.05	$53.00
Purchase #4	$105.44	12.426%	$118.542	$118.54	$118.55	$118.50
Purchase #5	$104.89	6.356%	$111.5568	$111.56	$111.55	$111.60
Purchase #6	$200.38	7.522%	$215.4526	$215.45	$215.45	$215.50
Purchase #7	$155.78	4.236%	$162.3788	$162.38	$162.40	$162.40
7 purchase totals =	$970.49		$1,047.5828	$1,047.59	$1,047.65	$1,047.60