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	$148.57	13.620%	$168.8052	$168.81	$168.80	$168.80
Purchase #2	$47.49	13.725%	$54.008	$54.01	$54.00	$54.00
Purchase #3	$87.39	5.800%	$92.4586	$92.46	$92.45	$92.50
Purchase #4	$172.80	11.253%	$192.2452	$192.25	$192.25	$192.20
Purchase #5	$113.64	13.819%	$129.3439	$129.34	$129.35	$129.30
Purchase #6	$224.32	7.545%	$241.2449	$241.24	$241.25	$241.20
Purchase #7	$73.30	7.524%	$78.8151	$78.82	$78.80	$78.80
7 purchase totals =	$867.51		$956.9209	$956.93	$956.90	$956.80