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	$219.30	5.601%	$231.583	$231.58	$231.60	$231.60
Purchase #2	$38.54	7.291%	$41.35	$41.35	$41.35	$41.40
Purchase #3	$152.85	5.732%	$161.6114	$161.61	$161.60	$161.60
Purchase #4	$213.35	12.581%	$240.1916	$240.19	$240.20	$240.20
Purchase #5	$104.60	13.214%	$118.4218	$118.42	$118.40	$118.40
Purchase #6	$179.72	9.523%	$196.8347	$196.83	$196.85	$196.80
Purchase #7	$192.51	3.269%	$198.8032	$198.80	$198.80	$198.80
7 purchase totals =	$1,100.87		$1,188.7957	$1,188.78	$1,188.80	$1,188.80