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	$131.94	12.511%	$148.447	$148.45	$148.45	$148.40
Purchase #2	$228.46	4.332%	$238.3569	$238.36	$238.35	$238.40
Purchase #3	$178.76	9.774%	$196.232	$196.23	$196.25	$196.20
Purchase #4	$241.30	12.806%	$272.2009	$272.20	$272.20	$272.20
Purchase #5	$203.54	11.693%	$227.3399	$227.34	$227.35	$227.30
Purchase #6	$204.52	13.388%	$231.9011	$231.90	$231.90	$231.90
Purchase #7	$176.69	9.138%	$192.8359	$192.84	$192.85	$192.80
7 purchase totals =	$1,365.21		$1,507.3137	$1,507.32	$1,507.35	$1,507.20