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	$10.73	11.328%	$11.9455	$11.95	$11.95	$11.90
Purchase #2	$28.71	9.534%	$31.4472	$31.45	$31.45	$31.40
Purchase #3	$32.90	6.148%	$34.9227	$34.92	$34.90	$34.90
Purchase #4	$59.41	6.579%	$63.3186	$63.32	$63.30	$63.30
Purchase #5	$131.86	5.682%	$139.3523	$139.35	$139.35	$139.40
Purchase #6	$78.83	7.581%	$84.8061	$84.81	$84.80	$84.80
Purchase #7	$128.38	3.710%	$133.1429	$133.14	$133.15	$133.10
7 purchase totals =	$470.82		$498.9353	$498.94	$498.90	$498.80