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	$205.40	5.113%	$215.9021	$215.90	$215.90	$215.90
Purchase #2	$81.38	11.164%	$90.4653	$90.47	$90.45	$90.50
Purchase #3	$39.53	9.209%	$43.1703	$43.17	$43.15	$43.20
Purchase #4	$44.49	6.307%	$47.296	$47.30	$47.30	$47.30
Purchase #5	$98.37	3.504%	$101.8169	$101.82	$101.80	$101.80
Purchase #6	$25.51	6.111%	$27.0689	$27.07	$27.05	$27.10
Purchase #7	$94.81	13.264%	$107.3856	$107.39	$107.40	$107.40
7 purchase totals =	$589.49		$633.1051	$633.12	$633.05	$633.20