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 $59.26   5.563%   $62.5566   $62.56   $62.55   $62.60  
  Purchase #2 $59.26   6.665%   $63.2097   $63.21   $63.20   $63.20  
  Purchase #3 $207.25   8.470%   $224.8041   $224.80   $224.80   $224.80  
  Purchase #4 $216.30   3.630%   $224.1517   $224.15   $224.15   $224.20  
  Purchase #5 $67.97   5.574%   $71.7586   $71.76   $71.75   $71.80  
  Purchase #6 $28.70   4.136%   $29.887   $29.89   $29.90   $29.90  
  Purchase #7 $14.89   5.112%   $15.6512   $15.65   $15.65   $15.70  
  7 purchase totals = $653.63       $692.0189   $692.02   $692.00   $692.20