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	$241.66	8.161%	$261.3819	$261.38	$261.40	$261.40
Purchase #2	$227.57	13.160%	$257.5182	$257.52	$257.50	$257.50
Purchase #3	$118.54	6.577%	$126.3364	$126.34	$126.35	$126.30
Purchase #4	$197.28	12.440%	$221.8216	$221.82	$221.80	$221.80
Purchase #5	$106.75	4.846%	$111.9231	$111.92	$111.90	$111.90
Purchase #6	$75.94	3.134%	$78.32	$78.32	$78.30	$78.30
Purchase #7	$22.70	8.264%	$24.5759	$24.58	$24.60	$24.60
7 purchase totals =	$990.44		$1,081.8771	$1,081.88	$1,081.85	$1,081.80