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	$55.72	13.174%	$63.0606	$63.06	$63.05	$63.10
Purchase #2	$221.50	12.143%	$248.3967	$248.40	$248.40	$248.40
Purchase #3	$51.66	7.850%	$55.7153	$55.72	$55.70	$55.70
Purchase #4	$52.81	13.329%	$59.849	$59.85	$59.85	$59.80
Purchase #5	$161.47	10.293%	$178.0901	$178.09	$178.10	$178.10
Purchase #6	$212.44	9.648%	$232.9362	$232.94	$232.95	$232.90
Purchase #7	$168.29	10.462%	$185.8965	$185.90	$185.90	$185.90
7 purchase totals =	$923.89		$1,023.9444	$1,023.96	$1,023.95	$1,023.90