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	$113.40	11.537%	$126.483	$126.48	$126.50	$126.50
Purchase #2	$217.67	4.292%	$227.0124	$227.01	$227.00	$227.00
Purchase #3	$177.59	10.681%	$196.5584	$196.56	$196.55	$196.60
Purchase #4	$19.72	3.581%	$20.4262	$20.43	$20.45	$20.40
Purchase #5	$211.87	13.680%	$240.8538	$240.85	$240.85	$240.90
Purchase #6	$9.66	7.856%	$10.4189	$10.42	$10.40	$10.40
Purchase #7	$63.48	4.461%	$66.3118	$66.31	$66.30	$66.30
7 purchase totals =	$813.39		$888.0645	$888.06	$888.05	$888.10