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	$187.45	9.682%	$205.5989	$205.60	$205.60	$205.60
Purchase #2	$165.60	5.484%	$174.6815	$174.68	$174.70	$174.70
Purchase #3	$123.83	6.499%	$131.8777	$131.88	$131.90	$131.90
Purchase #4	$52.43	12.775%	$59.1279	$59.13	$59.15	$59.10
Purchase #5	$86.89	3.775%	$90.1701	$90.17	$90.15	$90.20
Purchase #6	$188.39	12.854%	$212.6057	$212.61	$212.60	$212.60
Purchase #7	$97.51	3.359%	$100.7854	$100.79	$100.80	$100.80
7 purchase totals =	$902.10		$974.8472	$974.86	$974.90	$974.90