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	$78.39	8.549%	$85.0916	$85.09	$85.10	$85.10
Purchase #2	$98.76	4.320%	$103.0264	$103.03	$103.05	$103.00
Purchase #3	$103.77	13.607%	$117.89	$117.89	$117.90	$117.90
Purchase #4	$214.81	9.176%	$234.521	$234.52	$234.50	$234.50
Purchase #5	$237.70	10.354%	$262.3115	$262.31	$262.30	$262.30
Purchase #6	$213.86	5.465%	$225.5474	$225.55	$225.55	$225.50
Purchase #7	$24.36	13.505%	$27.6498	$27.65	$27.65	$27.60
7 purchase totals =	$971.65		$1,056.0377	$1,056.04	$1,056.05	$1,055.90