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	$5.25	3.594%	$5.4387	$5.44	$5.45	$5.40
Purchase #2	$247.56	4.456%	$258.5913	$258.59	$258.60	$258.60
Purchase #3	$181.49	8.276%	$196.5101	$196.51	$196.50	$196.50
Purchase #4	$35.92	12.326%	$40.3475	$40.35	$40.35	$40.30
Purchase #5	$33.51	12.618%	$37.7383	$37.74	$37.75	$37.70
Purchase #6	$180.37	3.356%	$186.4232	$186.42	$186.40	$186.40
Purchase #7	$57.93	8.808%	$63.0325	$63.03	$63.05	$63.00
7 purchase totals =	$742.03		$788.0816	$788.08	$788.10	$787.90