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	$158.72	3.870%	$164.8625	$164.86	$164.85	$164.90
Purchase #2	$40.39	13.203%	$45.7227	$45.72	$45.70	$45.70
Purchase #3	$117.31	7.773%	$126.4285	$126.43	$126.45	$126.40
Purchase #4	$168.71	8.478%	$183.0132	$183.01	$183.00	$183.00
Purchase #5	$15.65	13.270%	$17.7268	$17.73	$17.75	$17.70
Purchase #6	$11.33	10.174%	$12.4827	$12.48	$12.50	$12.50
Purchase #7	$148.34	13.462%	$168.3095	$168.31	$168.30	$168.30
7 purchase totals =	$660.45		$718.5459	$718.54	$718.55	$718.50