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	$117.71	5.289%	$123.9357	$123.94	$123.95	$123.90
Purchase #2	$144.61	5.536%	$152.6156	$152.62	$152.60	$152.60
Purchase #3	$199.79	7.285%	$214.3447	$214.34	$214.35	$214.30
Purchase #4	$78.42	12.113%	$87.919	$87.92	$87.90	$87.90
Purchase #5	$57.68	8.438%	$62.547	$62.55	$62.55	$62.50
Purchase #6	$227.53	8.845%	$247.655	$247.66	$247.65	$247.70
Purchase #7	$106.85	9.419%	$116.9142	$116.91	$116.90	$116.90
7 purchase totals =	$932.59		$1,005.9312	$1,005.94	$1,005.90	$1,005.80