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	$14.47	5.414%	$15.2534	$15.25	$15.25	$15.30
Purchase #2	$38.67	8.856%	$42.0946	$42.09	$42.10	$42.10
Purchase #3	$38.71	4.835%	$40.5816	$40.58	$40.60	$40.60
Purchase #4	$76.59	7.375%	$82.2385	$82.24	$82.25	$82.20
Purchase #5	$47.88	5.308%	$50.4215	$50.42	$50.40	$50.40
Purchase #6	$168.65	12.685%	$190.0433	$190.04	$190.05	$190.00
Purchase #7	$12.38	4.166%	$12.8958	$12.90	$12.90	$12.90
7 purchase totals =	$397.35		$433.5287	$433.52	$433.55	$433.50