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	$117.45	12.352%	$131.9574	$131.96	$131.95	$132.00
Purchase #2	$216.25	10.124%	$238.1432	$238.14	$238.15	$238.10
Purchase #3	$97.70	4.722%	$102.3134	$102.31	$102.30	$102.30
Purchase #4	$24.51	10.402%	$27.0595	$27.06	$27.05	$27.10
Purchase #5	$18.81	13.136%	$21.2809	$21.28	$21.30	$21.30
Purchase #6	$175.91	9.487%	$192.5986	$192.60	$192.60	$192.60
Purchase #7	$89.84	10.732%	$99.4816	$99.48	$99.50	$99.50
7 purchase totals =	$740.47		$812.8346	$812.83	$812.85	$812.90