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	$124.69	12.720%	$140.5506	$140.55	$140.55	$140.60
Purchase #2	$29.94	11.617%	$33.4181	$33.42	$33.40	$33.40
Purchase #3	$128.53	9.189%	$140.3406	$140.34	$140.35	$140.30
Purchase #4	$172.88	8.792%	$188.0796	$188.08	$188.10	$188.10
Purchase #5	$39.69	8.438%	$43.039	$43.04	$43.05	$43.00
Purchase #6	$20.38	10.731%	$22.567	$22.57	$22.55	$22.60
Purchase #7	$207.40	5.381%	$218.5602	$218.56	$218.55	$218.60
7 purchase totals =	$723.51		$786.5551	$786.56	$786.55	$786.60