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	$208.71	10.791%	$231.2319	$231.23	$231.25	$231.20
Purchase #2	$82.57	9.298%	$90.2474	$90.25	$90.25	$90.20
Purchase #3	$225.30	10.712%	$249.4341	$249.43	$249.45	$249.40
Purchase #4	$11.52	12.296%	$12.9365	$12.94	$12.95	$12.90
Purchase #5	$234.72	7.493%	$252.3076	$252.31	$252.30	$252.30
Purchase #6	$28.29	12.469%	$31.8175	$31.82	$31.80	$31.80
Purchase #7	$168.76	7.611%	$181.6043	$181.60	$181.60	$181.60
7 purchase totals =	$959.87		$1,049.5793	$1,049.58	$1,049.60	$1,049.40