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	$43.57	7.396%	$46.7924	$46.79	$46.80	$46.80
Purchase #2	$95.96	3.716%	$99.5259	$99.53	$99.55	$99.50
Purchase #3	$145.78	7.412%	$156.5852	$156.59	$156.60	$156.60
Purchase #4	$28.61	4.493%	$29.8954	$29.90	$29.90	$29.90
Purchase #5	$19.89	3.659%	$20.6178	$20.62	$20.60	$20.60
Purchase #6	$246.47	13.684%	$280.197	$280.20	$280.20	$280.20
Purchase #7	$110.48	9.420%	$120.8872	$120.89	$120.90	$120.90
7 purchase totals =	$690.76		$754.5009	$754.52	$754.55	$754.50