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	$239.86	3.816%	$249.0131	$249.01	$249.00	$249.00
Purchase #2	$93.55	12.489%	$105.2335	$105.23	$105.25	$105.20
Purchase #3	$14.54	9.731%	$15.9549	$15.95	$15.95	$16.00
Purchase #4	$244.60	5.149%	$257.1945	$257.19	$257.20	$257.20
Purchase #5	$162.69	9.783%	$178.606	$178.61	$178.60	$178.60
Purchase #6	$42.50	7.105%	$45.5196	$45.52	$45.50	$45.50
Purchase #7	$153.97	9.392%	$168.4309	$168.43	$168.45	$168.40
7 purchase totals =	$951.71		$1,019.9525	$1,019.94	$1,019.95	$1,019.90