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	$45.42	4.764%	$47.5838	$47.58	$47.60	$47.60
Purchase #2	$86.67	4.354%	$90.4436	$90.44	$90.45	$90.40
Purchase #3	$144.47	13.709%	$164.2754	$164.28	$164.30	$164.30
Purchase #4	$66.52	5.437%	$70.1367	$70.14	$70.15	$70.10
Purchase #5	$204.64	5.688%	$216.2799	$216.28	$216.30	$216.30
Purchase #6	$113.34	9.127%	$123.6845	$123.68	$123.70	$123.70
Purchase #7	$149.98	3.593%	$155.3688	$155.37	$155.35	$155.40
7 purchase totals =	$811.04		$867.7727	$867.77	$867.85	$867.80