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	$228.34	5.595%	$241.1156	$241.12	$241.10	$241.10
Purchase #2	$102.50	6.810%	$109.4803	$109.48	$109.50	$109.50
Purchase #3	$23.48	3.401%	$24.2786	$24.28	$24.30	$24.30
Purchase #4	$78.78	13.758%	$89.6186	$89.62	$89.60	$89.60
Purchase #5	$35.38	9.396%	$38.7043	$38.70	$38.70	$38.70
Purchase #6	$49.32	5.163%	$51.8664	$51.87	$51.85	$51.90
Purchase #7	$141.93	8.714%	$154.2978	$154.30	$154.30	$154.30
7 purchase totals =	$659.73		$709.3616	$709.37	$709.35	$709.40