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	$238.34	9.869%	$261.8618	$261.86	$261.85	$261.90
Purchase #2	$205.97	11.407%	$229.465	$229.47	$229.45	$229.50
Purchase #3	$90.76	4.511%	$94.8542	$94.85	$94.85	$94.90
Purchase #4	$112.86	7.633%	$121.4746	$121.47	$121.45	$121.50
Purchase #5	$45.61	13.102%	$51.5858	$51.59	$51.60	$51.60
Purchase #6	$154.62	6.293%	$164.3502	$164.35	$164.35	$164.40
Purchase #7	$126.66	9.160%	$138.2621	$138.26	$138.25	$138.30
7 purchase totals =	$974.82		$1,061.8537	$1,061.85	$1,061.80	$1,062.10