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	$10.44	9.719%	$11.4547	$11.45	$11.45	$11.50
Purchase #2	$152.86	6.661%	$163.042	$163.04	$163.05	$163.00
Purchase #3	$128.86	10.688%	$142.6326	$142.63	$142.65	$142.60
Purchase #4	$211.47	5.132%	$222.3226	$222.32	$222.30	$222.30
Purchase #5	$139.85	6.153%	$148.455	$148.46	$148.45	$148.50
Purchase #6	$214.52	12.619%	$241.5903	$241.59	$241.60	$241.60
Purchase #7	$65.78	13.357%	$74.5662	$74.57	$74.55	$74.60
7 purchase totals =	$923.78		$1,004.0634	$1,004.06	$1,004.05	$1,004.10