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	$10.40	10.274%	$11.4685	$11.47	$11.45	$11.50
Purchase #2	$177.29	10.638%	$196.1501	$196.15	$196.15	$196.20
Purchase #3	$41.85	4.855%	$43.8818	$43.88	$43.90	$43.90
Purchase #4	$105.46	11.326%	$117.4044	$117.40	$117.40	$117.40
Purchase #5	$29.38	5.835%	$31.0943	$31.09	$31.10	$31.10
Purchase #6	$94.38	7.308%	$101.2773	$101.28	$101.30	$101.30
Purchase #7	$96.25	4.329%	$100.4167	$100.42	$100.40	$100.40
7 purchase totals =	$555.01		$601.6931	$601.69	$601.70	$601.80