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	$62.35	7.188%	$66.8317	$66.83	$66.85	$66.80
Purchase #2	$46.29	12.500%	$52.0763	$52.08	$52.10	$52.10
Purchase #3	$172.51	3.527%	$178.5944	$178.59	$178.60	$178.60
Purchase #4	$70.51	11.470%	$78.5975	$78.60	$78.60	$78.60
Purchase #5	$125.63	11.421%	$139.9782	$139.98	$140.00	$140.00
Purchase #6	$121.39	12.404%	$136.4472	$136.45	$136.45	$136.40
Purchase #7	$56.36	7.244%	$60.4427	$60.44	$60.45	$60.40
7 purchase totals =	$655.04		$712.9680	$712.97	$713.05	$712.90