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	$75.58	9.608%	$82.8417	$82.84	$82.85	$82.80
Purchase #2	$90.32	7.402%	$97.0055	$97.01	$97.00	$97.00
Purchase #3	$28.64	8.554%	$31.0899	$31.09	$31.10	$31.10
Purchase #4	$188.26	10.619%	$208.2513	$208.25	$208.25	$208.30
Purchase #5	$49.64	8.822%	$54.0192	$54.02	$54.00	$54.00
Purchase #6	$153.90	9.575%	$168.6359	$168.64	$168.65	$168.60
Purchase #7	$18.88	11.477%	$21.0469	$21.05	$21.05	$21.00
7 purchase totals =	$605.22		$662.8904	$662.90	$662.90	$662.80