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	$62.82	4.320%	$65.5338	$65.53	$65.55	$65.50
Purchase #2	$40.37	7.778%	$43.51	$43.51	$43.50	$43.50
Purchase #3	$150.35	3.375%	$155.4243	$155.42	$155.40	$155.40
Purchase #4	$106.94	3.602%	$110.792	$110.79	$110.80	$110.80
Purchase #5	$107.26	8.549%	$116.4297	$116.43	$116.45	$116.40
Purchase #6	$247.80	3.274%	$255.913	$255.91	$255.90	$255.90
Purchase #7	$28.59	9.839%	$31.403	$31.40	$31.40	$31.40
7 purchase totals =	$744.13		$779.0058	$778.99	$779.00	$778.90