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	$30.32	4.106%	$31.5649	$31.56	$31.55	$31.60
Purchase #2	$86.37	5.173%	$90.8379	$90.84	$90.85	$90.80
Purchase #3	$168.90	5.713%	$178.5493	$178.55	$178.55	$178.50
Purchase #4	$192.96	12.874%	$217.8017	$217.80	$217.80	$217.80
Purchase #5	$176.32	9.820%	$193.6346	$193.63	$193.65	$193.60
Purchase #6	$200.43	10.267%	$221.0081	$221.01	$221.00	$221.00
Purchase #7	$88.57	4.849%	$92.8648	$92.86	$92.85	$92.90
7 purchase totals =	$943.87		$1,026.2613	$1,026.25	$1,026.25	$1,026.20