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	$157.90	12.630%	$177.8428	$177.84	$177.85	$177.80
Purchase #2	$159.68	7.617%	$171.8428	$171.84	$171.85	$171.80
Purchase #3	$76.40	3.229%	$78.867	$78.87	$78.85	$78.90
Purchase #4	$45.96	3.438%	$47.5401	$47.54	$47.55	$47.50
Purchase #5	$201.69	9.758%	$221.3709	$221.37	$221.35	$221.40
Purchase #6	$140.89	6.816%	$150.4931	$150.49	$150.50	$150.50
Purchase #7	$20.40	5.590%	$21.5404	$21.54	$21.55	$21.50
7 purchase totals =	$802.92		$869.4971	$869.49	$869.50	$869.40