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	$46.65	11.617%	$52.0693	$52.07	$52.05	$52.10
Purchase #2	$20.52	5.618%	$21.6728	$21.67	$21.65	$21.70
Purchase #3	$69.97	5.361%	$73.7211	$73.72	$73.70	$73.70
Purchase #4	$140.46	7.360%	$150.7979	$150.80	$150.80	$150.80
Purchase #5	$87.37	3.528%	$90.4524	$90.45	$90.45	$90.50
Purchase #6	$188.42	10.398%	$208.0119	$208.01	$208.00	$208.00
Purchase #7	$231.44	13.245%	$262.0942	$262.09	$262.10	$262.10
7 purchase totals =	$784.83		$858.8196	$858.81	$858.75	$858.90