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	$96.59	7.617%	$103.9473	$103.95	$103.95	$103.90
Purchase #2	$46.85	11.473%	$52.2251	$52.23	$52.25	$52.20
Purchase #3	$138.91	3.307%	$143.5038	$143.50	$143.50	$143.50
Purchase #4	$81.74	7.520%	$87.8868	$87.89	$87.90	$87.90
Purchase #5	$211.66	11.304%	$235.586	$235.59	$235.60	$235.60
Purchase #6	$40.90	10.824%	$45.327	$45.33	$45.35	$45.30
Purchase #7	$147.49	11.202%	$164.0118	$164.01	$164.00	$164.00
7 purchase totals =	$764.14		$832.4878	$832.50	$832.55	$832.40