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	$208.49	4.508%	$217.8887	$217.89	$217.90	$217.90
Purchase #2	$31.41	10.116%	$34.5874	$34.59	$34.60	$34.60
Purchase #3	$221.40	4.739%	$231.8921	$231.89	$231.90	$231.90
Purchase #4	$39.49	7.756%	$42.5528	$42.55	$42.55	$42.60
Purchase #5	$235.86	11.476%	$262.9273	$262.93	$262.95	$262.90
Purchase #6	$236.51	10.321%	$260.9202	$260.92	$260.90	$260.90
Purchase #7	$131.70	12.850%	$148.6235	$148.62	$148.60	$148.60
7 purchase totals =	$1,104.86		$1,199.3920	$1,199.39	$1,199.40	$1,199.40