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	$214.70	12.470%	$241.4731	$241.47	$241.45	$241.50
Purchase #2	$116.58	9.349%	$127.4791	$127.48	$127.50	$127.50
Purchase #3	$231.42	10.837%	$256.499	$256.50	$256.50	$256.50
Purchase #4	$239.79	9.479%	$262.5197	$262.52	$262.50	$262.50
Purchase #5	$117.83	4.665%	$123.3268	$123.33	$123.35	$123.30
Purchase #6	$240.74	3.585%	$249.3705	$249.37	$249.35	$249.40
Purchase #7	$178.39	4.725%	$186.8189	$186.82	$186.80	$186.80
7 purchase totals =	$1,339.45		$1,447.4871	$1,447.49	$1,447.45	$1,447.50