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	$219.87	13.457%	$249.4579	$249.46	$249.45	$249.50
Purchase #2	$25.49	9.569%	$27.9291	$27.93	$27.95	$27.90
Purchase #3	$230.85	11.161%	$256.6152	$256.62	$256.60	$256.60
Purchase #4	$62.94	11.156%	$69.9616	$69.96	$69.95	$70.00
Purchase #5	$173.60	9.779%	$190.5763	$190.58	$190.60	$190.60
Purchase #6	$119.52	9.786%	$131.2162	$131.22	$131.20	$131.20
Purchase #7	$198.54	13.438%	$225.2198	$225.22	$225.20	$225.20
7 purchase totals =	$1,030.81		$1,150.9761	$1,150.99	$1,150.95	$1,151.00