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	$163.98	10.584%	$181.3356	$181.34	$181.35	$181.30
Purchase #2	$164.72	11.758%	$184.0878	$184.09	$184.10	$184.10
Purchase #3	$68.83	11.144%	$76.5004	$76.50	$76.50	$76.50
Purchase #4	$84.84	11.375%	$94.4906	$94.49	$94.50	$94.50
Purchase #5	$176.40	6.271%	$187.462	$187.46	$187.45	$187.50
Purchase #6	$132.33	13.590%	$150.3136	$150.31	$150.30	$150.30
Purchase #7	$41.93	4.487%	$43.8114	$43.81	$43.80	$43.80
7 purchase totals =	$833.03		$918.0014	$918.00	$918.00	$918.00