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 $60.76   4.680%   $63.6036   $63.60   $63.60   $63.60  
  Purchase #2 $22.31   13.272%   $25.271   $25.27   $25.25   $25.30  
  Purchase #3 $63.49   5.666%   $67.0873   $67.09   $67.10   $67.10  
  Purchase #4 $105.48   5.784%   $111.581   $111.58   $111.60   $111.60  
  Purchase #5 $245.71   10.506%   $271.5243   $271.52   $271.50   $271.50  
  Purchase #6 $117.44   4.120%   $122.2785   $122.28   $122.30   $122.30  
  Purchase #7 $190.72   5.471%   $201.1543   $201.15   $201.15   $201.20  
  7 purchase totals = $805.91       $862.5000   $862.49   $862.50   $862.60