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	$250.44	9.579%	$274.4296	$274.43	$274.45	$274.40
Purchase #2	$239.82	8.561%	$260.351	$260.35	$260.35	$260.40
Purchase #3	$127.30	10.859%	$141.1235	$141.12	$141.10	$141.10
Purchase #4	$13.61	12.200%	$15.2704	$15.27	$15.25	$15.30
Purchase #5	$7.79	4.546%	$8.1441	$8.14	$8.15	$8.10
Purchase #6	$220.59	5.870%	$233.5386	$233.54	$233.55	$233.50
Purchase #7	$103.57	7.298%	$111.1285	$111.13	$111.15	$111.10
7 purchase totals =	$963.12		$1,043.9857	$1,043.98	$1,044.00	$1,043.90