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	$217.55	9.630%	$238.5001	$238.50	$238.50	$238.50
Purchase #2	$170.57	5.498%	$179.9479	$179.95	$179.95	$179.90
Purchase #3	$95.30	7.871%	$102.8011	$102.80	$102.80	$102.80
Purchase #4	$60.85	3.719%	$63.113	$63.11	$63.10	$63.10
Purchase #5	$153.90	3.228%	$158.8679	$158.87	$158.85	$158.90
Purchase #6	$127.49	9.409%	$139.4855	$139.49	$139.50	$139.50
Purchase #7	$126.53	5.852%	$133.9345	$133.93	$133.95	$133.90
7 purchase totals =	$952.19		$1,016.6500	$1,016.65	$1,016.65	$1,016.60