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	$231.85	13.362%	$262.8298	$262.83	$262.85	$262.80
Purchase #2	$217.80	3.226%	$224.8262	$224.83	$224.85	$224.80
Purchase #3	$133.75	6.824%	$142.8771	$142.88	$142.90	$142.90
Purchase #4	$56.48	12.193%	$63.3666	$63.37	$63.35	$63.40
Purchase #5	$98.86	3.243%	$102.066	$102.07	$102.05	$102.10
Purchase #6	$240.63	6.163%	$255.46	$255.46	$255.45	$255.50
Purchase #7	$64.73	3.302%	$66.8674	$66.87	$66.85	$66.90
7 purchase totals =	$1,044.10		$1,118.2931	$1,118.31	$1,118.30	$1,118.40