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	$96.60	9.214%	$105.5007	$105.50	$105.50	$105.50
Purchase #2	$33.88	12.575%	$38.1404	$38.14	$38.15	$38.10
Purchase #3	$238.25	3.537%	$246.6769	$246.68	$246.70	$246.70
Purchase #4	$206.91	4.638%	$216.5065	$216.51	$216.50	$216.50
Purchase #5	$95.36	5.778%	$100.8699	$100.87	$100.85	$100.90
Purchase #6	$179.83	4.476%	$187.8792	$187.88	$187.90	$187.90
Purchase #7	$202.46	9.868%	$222.4388	$222.44	$222.45	$222.40
7 purchase totals =	$1,053.29		$1,118.0124	$1,118.02	$1,118.05	$1,118.00