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	$151.70	3.451%	$156.9352	$156.94	$156.95	$156.90
Purchase #2	$250.88	3.778%	$260.3582	$260.36	$260.35	$260.40
Purchase #3	$164.38	9.235%	$179.5605	$179.56	$179.55	$179.60
Purchase #4	$104.52	7.554%	$112.4154	$112.42	$112.40	$112.40
Purchase #5	$55.25	9.715%	$60.6175	$60.62	$60.60	$60.60
Purchase #6	$59.79	11.826%	$66.8608	$66.86	$66.85	$66.90
Purchase #7	$57.38	10.571%	$63.4456	$63.45	$63.45	$63.40
7 purchase totals =	$843.90		$900.1932	$900.21	$900.15	$900.20