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	$205.85	6.771%	$219.7881	$219.79	$219.80	$219.80
Purchase #2	$195.86	12.874%	$221.075	$221.08	$221.10	$221.10
Purchase #3	$227.37	7.532%	$244.4955	$244.50	$244.50	$244.50
Purchase #4	$65.61	11.105%	$72.896	$72.90	$72.90	$72.90
Purchase #5	$183.53	8.773%	$199.6311	$199.63	$199.65	$199.60
Purchase #6	$73.61	13.108%	$83.2588	$83.26	$83.25	$83.30
Purchase #7	$82.54	9.464%	$90.3516	$90.35	$90.35	$90.40
7 purchase totals =	$1,034.37		$1,131.4961	$1,131.51	$1,131.55	$1,131.60