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	$72.60	8.165%	$78.5278	$78.53	$78.55	$78.50
Purchase #2	$189.99	9.638%	$208.3012	$208.30	$208.30	$208.30
Purchase #3	$48.47	10.725%	$53.6684	$53.67	$53.65	$53.70
Purchase #4	$222.64	3.242%	$229.858	$229.86	$229.85	$229.90
Purchase #5	$9.56	4.681%	$10.0075	$10.01	$10.00	$10.00
Purchase #6	$103.94	5.255%	$109.402	$109.40	$109.40	$109.40
Purchase #7	$187.92	4.726%	$196.8011	$196.80	$196.80	$196.80
7 purchase totals =	$835.12		$886.5660	$886.57	$886.55	$886.60