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	$118.45	4.308%	$123.5528	$123.55	$123.55	$123.60
Purchase #2	$209.83	13.506%	$238.1696	$238.17	$238.15	$238.20
Purchase #3	$177.71	3.849%	$184.5501	$184.55	$184.55	$184.60
Purchase #4	$65.69	9.729%	$72.081	$72.08	$72.10	$72.10
Purchase #5	$14.81	8.455%	$16.0622	$16.06	$16.05	$16.10
Purchase #6	$142.88	13.540%	$162.226	$162.23	$162.25	$162.20
Purchase #7	$127.35	8.527%	$138.2091	$138.21	$138.20	$138.20
7 purchase totals =	$856.72		$934.8508	$934.85	$934.85	$935.00