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	$183.50	11.858%	$205.2594	$205.26	$205.25	$205.30
Purchase #2	$63.89	7.762%	$68.8491	$68.85	$68.85	$68.80
Purchase #3	$94.46	9.241%	$103.189	$103.19	$103.20	$103.20
Purchase #4	$225.83	6.565%	$240.6557	$240.66	$240.65	$240.70
Purchase #5	$182.26	4.526%	$190.5091	$190.51	$190.50	$190.50
Purchase #6	$29.86	6.874%	$31.9126	$31.91	$31.90	$31.90
Purchase #7	$148.45	13.620%	$168.6689	$168.67	$168.65	$168.70
7 purchase totals =	$928.25		$1,009.0438	$1,009.05	$1,009.00	$1,009.10