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	$140.61	7.290%	$150.8605	$150.86	$150.85	$150.90
Purchase #2	$14.61	5.189%	$15.3681	$15.37	$15.35	$15.40
Purchase #3	$103.26	12.621%	$116.2924	$116.29	$116.30	$116.30
Purchase #4	$120.94	5.817%	$127.9751	$127.98	$128.00	$128.00
Purchase #5	$77.51	11.137%	$86.1423	$86.14	$86.15	$86.10
Purchase #6	$148.97	10.431%	$164.5091	$164.51	$164.50	$164.50
Purchase #7	$43.95	10.470%	$48.5516	$48.55	$48.55	$48.60
7 purchase totals =	$649.85		$709.6991	$709.70	$709.70	$709.80