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	$185.66	7.730%	$200.0115	$200.01	$200.00	$200.00
Purchase #2	$54.90	3.725%	$56.945	$56.95	$56.95	$56.90
Purchase #3	$196.50	12.509%	$221.0802	$221.08	$221.10	$221.10
Purchase #4	$246.82	9.242%	$269.6311	$269.63	$269.65	$269.60
Purchase #5	$183.75	4.798%	$192.5663	$192.57	$192.55	$192.60
Purchase #6	$94.51	10.547%	$104.478	$104.48	$104.50	$104.50
Purchase #7	$78.25	5.597%	$82.6297	$82.63	$82.65	$82.60
7 purchase totals =	$1,040.39		$1,127.3418	$1,127.35	$1,127.40	$1,127.30