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 $246.86   5.818%   $261.2223   $261.22   $261.20   $261.20  
  Purchase #2 $132.50   5.873%   $140.2817   $140.28   $140.30   $140.30  
  Purchase #3 $25.49   3.572%   $26.4005   $26.40   $26.40   $26.40  
  Purchase #4 $230.45   12.207%   $258.581   $258.58   $258.60   $258.60  
  Purchase #5 $152.93   6.245%   $162.4805   $162.48   $162.50   $162.50  
  Purchase #6 $142.51   9.246%   $155.6865   $155.69   $155.70   $155.70  
  Purchase #7 $195.92   4.474%   $204.6855   $204.69   $204.70   $204.70  
  7 purchase totals = $1,126.66       $1,209.3380   $1,209.34   $1,209.40   $1,209.40