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	$40.32	7.196%	$43.2214	$43.22	$43.20	$43.20
Purchase #2	$56.50	12.175%	$63.3789	$63.38	$63.40	$63.40
Purchase #3	$179.70	4.572%	$187.9159	$187.92	$187.90	$187.90
Purchase #4	$33.60	13.840%	$38.2502	$38.25	$38.25	$38.30
Purchase #5	$85.39	10.774%	$94.5899	$94.59	$94.60	$94.60
Purchase #6	$98.82	4.667%	$103.4319	$103.43	$103.45	$103.40
Purchase #7	$130.34	11.653%	$145.5285	$145.53	$145.55	$145.50
7 purchase totals =	$624.67		$676.3167	$676.32	$676.35	$676.30