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	$213.40	4.161%	$222.2796	$222.28	$222.30	$222.30
Purchase #2	$207.76	3.617%	$215.2747	$215.27	$215.25	$215.30
Purchase #3	$191.38	3.767%	$198.5893	$198.59	$198.60	$198.60
Purchase #4	$50.76	9.112%	$55.3853	$55.39	$55.40	$55.40
Purchase #5	$69.42	13.625%	$78.8785	$78.88	$78.90	$78.90
Purchase #6	$170.85	6.863%	$182.5754	$182.58	$182.60	$182.60
Purchase #7	$44.39	6.551%	$47.298	$47.30	$47.30	$47.30
7 purchase totals =	$947.96		$1,000.2808	$1,000.29	$1,000.35	$1,000.40