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	$62.38	6.709%	$66.5651	$66.57	$66.55	$66.60
Purchase #2	$10.28	6.570%	$10.9554	$10.96	$10.95	$11.00
Purchase #3	$20.67	4.736%	$21.6489	$21.65	$21.65	$21.60
Purchase #4	$137.82	10.708%	$152.5778	$152.58	$152.60	$152.60
Purchase #5	$67.65	6.545%	$72.0777	$72.08	$72.10	$72.10
Purchase #6	$127.70	12.309%	$143.4186	$143.42	$143.40	$143.40
Purchase #7	$209.44	4.262%	$218.3663	$218.37	$218.35	$218.40
7 purchase totals =	$635.94		$685.6098	$685.63	$685.60	$685.70