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	$48.63	11.771%	$54.3542	$54.35	$54.35	$54.40
Purchase #2	$167.48	10.693%	$185.3886	$185.39	$185.40	$185.40
Purchase #3	$185.43	6.156%	$196.8451	$196.85	$196.85	$196.80
Purchase #4	$180.82	13.829%	$205.8256	$205.83	$205.85	$205.80
Purchase #5	$51.50	5.828%	$54.5014	$54.50	$54.50	$54.50
Purchase #6	$160.92	11.214%	$178.9656	$178.97	$178.95	$179.00
Purchase #7	$6.76	3.744%	$7.0131	$7.01	$7.00	$7.00
7 purchase totals =	$801.54		$882.8936	$882.90	$882.90	$882.90