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	$115.69	8.721%	$125.7793	$125.78	$125.80	$125.80
Purchase #2	$127.94	4.340%	$133.4926	$133.49	$133.50	$133.50
Purchase #3	$232.98	10.745%	$258.0137	$258.01	$258.00	$258.00
Purchase #4	$40.39	13.529%	$45.8544	$45.85	$45.85	$45.90
Purchase #5	$129.44	10.226%	$142.6765	$142.68	$142.70	$142.70
Purchase #6	$224.41	13.712%	$255.1811	$255.18	$255.20	$255.20
Purchase #7	$86.98	13.120%	$98.3918	$98.39	$98.40	$98.40
7 purchase totals =	$957.83		$1,059.3894	$1,059.38	$1,059.45	$1,059.50