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	$160.59	4.858%	$168.3915	$168.39	$168.40	$168.40
Purchase #2	$66.74	9.271%	$72.9275	$72.93	$72.95	$72.90
Purchase #3	$104.95	6.564%	$111.8389	$111.84	$111.85	$111.80
Purchase #4	$62.45	6.813%	$66.7047	$66.70	$66.70	$66.70
Purchase #5	$249.57	3.656%	$258.6943	$258.69	$258.70	$258.70
Purchase #6	$215.25	8.200%	$232.9005	$232.90	$232.90	$232.90
Purchase #7	$111.92	12.653%	$126.0812	$126.08	$126.10	$126.10
7 purchase totals =	$971.47		$1,037.5386	$1,037.53	$1,037.60	$1,037.50