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	$74.39	11.159%	$82.6912	$82.69	$82.70	$82.70
Purchase #2	$158.38	5.705%	$167.4156	$167.42	$167.40	$167.40
Purchase #3	$68.37	3.249%	$70.5913	$70.59	$70.60	$70.60
Purchase #4	$194.59	11.187%	$216.3588	$216.36	$216.35	$216.40
Purchase #5	$49.86	9.378%	$54.5359	$54.54	$54.55	$54.50
Purchase #6	$176.84	7.708%	$190.4708	$190.47	$190.45	$190.50
Purchase #7	$207.37	11.697%	$231.6261	$231.63	$231.65	$231.60
7 purchase totals =	$929.80		$1,013.6897	$1,013.70	$1,013.70	$1,013.70