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	$156.60	3.873%	$162.6651	$162.67	$162.65	$162.70
Purchase #2	$86.67	4.590%	$90.6482	$90.65	$90.65	$90.60
Purchase #3	$83.59	8.723%	$90.8816	$90.88	$90.90	$90.90
Purchase #4	$153.53	8.179%	$166.0872	$166.09	$166.10	$166.10
Purchase #5	$183.57	7.786%	$197.8628	$197.86	$197.85	$197.90
Purchase #6	$36.93	4.127%	$38.4541	$38.45	$38.45	$38.50
Purchase #7	$30.79	3.364%	$31.8258	$31.83	$31.85	$31.80
7 purchase totals =	$731.68		$778.4248	$778.43	$778.45	$778.50