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	$69.98	12.156%	$78.4868	$78.49	$78.50	$78.50
Purchase #2	$13.78	4.623%	$14.417	$14.42	$14.40	$14.40
Purchase #3	$60.42	4.666%	$63.2392	$63.24	$63.25	$63.20
Purchase #4	$51.57	13.475%	$58.5191	$58.52	$58.50	$58.50
Purchase #5	$68.80	4.500%	$71.896	$71.90	$71.90	$71.90
Purchase #6	$80.32	13.159%	$90.8893	$90.89	$90.90	$90.90
Purchase #7	$182.61	10.296%	$201.4115	$201.41	$201.40	$201.40
7 purchase totals =	$527.48		$578.8589	$578.87	$578.85	$578.80