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	$86.30	3.538%	$89.3533	$89.35	$89.35	$89.40
Purchase #2	$136.31	4.429%	$142.3472	$142.35	$142.35	$142.30
Purchase #3	$241.66	13.484%	$274.2454	$274.25	$274.25	$274.20
Purchase #4	$180.37	11.205%	$200.5805	$200.58	$200.60	$200.60
Purchase #5	$190.59	9.632%	$208.9476	$208.95	$208.95	$208.90
Purchase #6	$96.78	12.203%	$108.5901	$108.59	$108.60	$108.60
Purchase #7	$104.55	12.351%	$117.463	$117.46	$117.45	$117.50
7 purchase totals =	$1,036.56		$1,141.5271	$1,141.53	$1,141.55	$1,141.50