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	$219.59	9.380%	$240.1875	$240.19	$240.20	$240.20
Purchase #2	$153.41	8.536%	$166.5051	$166.51	$166.50	$166.50
Purchase #3	$227.81	6.271%	$242.096	$242.10	$242.10	$242.10
Purchase #4	$63.98	5.630%	$67.5821	$67.58	$67.60	$67.60
Purchase #5	$101.25	4.211%	$105.5136	$105.51	$105.50	$105.50
Purchase #6	$152.76	6.686%	$162.9735	$162.97	$162.95	$163.00
Purchase #7	$66.65	9.256%	$72.8191	$72.82	$72.80	$72.80
7 purchase totals =	$985.45		$1,057.6769	$1,057.68	$1,057.65	$1,057.70