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	$156.63	5.284%	$164.9063	$164.91	$164.90	$164.90
Purchase #2	$77.33	6.785%	$82.5768	$82.58	$82.60	$82.60
Purchase #3	$22.73	10.373%	$25.0878	$25.09	$25.10	$25.10
Purchase #4	$70.89	10.597%	$78.4022	$78.40	$78.40	$78.40
Purchase #5	$161.66	9.271%	$176.6475	$176.65	$176.65	$176.60
Purchase #6	$115.85	7.544%	$124.5897	$124.59	$124.60	$124.60
Purchase #7	$113.45	11.393%	$126.3754	$126.38	$126.40	$126.40
7 purchase totals =	$718.54		$778.5857	$778.60	$778.65	$778.60