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 $52.39   8.698%   $56.9469   $56.95   $56.95   $56.90  
  Purchase #2 $71.32   6.294%   $75.8089   $75.81   $75.80   $75.80  
  Purchase #3 $116.68   8.797%   $126.9443   $126.94   $126.95   $126.90  
  Purchase #4 $245.46   6.518%   $261.4591   $261.46   $261.45   $261.50  
  Purchase #5 $187.96   8.206%   $203.384   $203.38   $203.40   $203.40  
  Purchase #6 $209.78   6.262%   $222.9164   $222.92   $222.90   $222.90  
  Purchase #7 $162.73   7.462%   $174.8729   $174.87   $174.85   $174.90  
  7 purchase totals = $1,046.32       $1,122.3325   $1,122.33   $1,122.30   $1,122.30