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	$219.93	11.163%	$244.4808	$244.48	$244.50	$244.50
Purchase #2	$185.82	5.706%	$196.4229	$196.42	$196.40	$196.40
Purchase #3	$174.83	6.683%	$186.5139	$186.51	$186.50	$186.50
Purchase #4	$112.28	9.160%	$122.5648	$122.56	$122.55	$122.60
Purchase #5	$40.64	7.598%	$43.7278	$43.73	$43.75	$43.70
Purchase #6	$39.73	5.192%	$41.7928	$41.79	$41.80	$41.80
Purchase #7	$83.46	13.738%	$94.9257	$94.93	$94.95	$94.90
7 purchase totals =	$856.69		$930.4287	$930.42	$930.45	$930.40