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	$82.25	4.384%	$85.8558	$85.86	$85.85	$85.90
Purchase #2	$109.52	6.853%	$117.0254	$117.03	$117.05	$117.00
Purchase #3	$132.37	9.805%	$145.3489	$145.35	$145.35	$145.30
Purchase #4	$100.40	10.762%	$111.205	$111.21	$111.20	$111.20
Purchase #5	$152.70	10.372%	$168.538	$168.54	$168.55	$168.50
Purchase #6	$96.92	6.249%	$102.9765	$102.98	$103.00	$103.00
Purchase #7	$157.72	11.112%	$175.2458	$175.25	$175.25	$175.20
7 purchase totals =	$831.88		$906.1954	$906.22	$906.25	$906.10