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	$247.59	6.132%	$262.7722	$262.77	$262.75	$262.80
Purchase #2	$111.48	10.509%	$123.1954	$123.20	$123.20	$123.20
Purchase #3	$51.57	6.636%	$54.9922	$54.99	$55.00	$55.00
Purchase #4	$97.42	3.220%	$100.5569	$100.56	$100.55	$100.60
Purchase #5	$115.55	7.710%	$124.4589	$124.46	$124.45	$124.50
Purchase #6	$102.83	10.364%	$113.4873	$113.49	$113.50	$113.50
Purchase #7	$219.93	3.408%	$227.4252	$227.43	$227.45	$227.40
7 purchase totals =	$946.37		$1,006.8881	$1,006.90	$1,006.90	$1,007.00