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	$36.62	10.333%	$40.4039	$40.40	$40.40	$40.40
Purchase #2	$152.61	3.504%	$157.9575	$157.96	$157.95	$158.00
Purchase #3	$127.37	11.710%	$142.285	$142.29	$142.30	$142.30
Purchase #4	$226.70	4.509%	$236.9219	$236.92	$236.90	$236.90
Purchase #5	$102.72	8.517%	$111.4687	$111.47	$111.45	$111.50
Purchase #6	$117.66	10.559%	$130.0837	$130.08	$130.10	$130.10
Purchase #7	$112.34	5.534%	$118.5569	$118.56	$118.55	$118.60
7 purchase totals =	$876.02		$937.6776	$937.68	$937.65	$937.80