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 $67.84   5.302%   $71.4369   $71.44   $71.45   $71.40  
  Purchase #2 $208.65   7.192%   $223.6561   $223.66   $223.65   $223.70  
  Purchase #3 $75.54   6.809%   $80.6835   $80.68   $80.70   $80.70  
  Purchase #4 $229.30   13.840%   $261.0351   $261.04   $261.05   $261.00  
  Purchase #5 $242.61   6.443%   $258.2414   $258.24   $258.25   $258.20  
  Purchase #6 $67.44   12.689%   $75.9975   $76.00   $76.00   $76.00  
  Purchase #7 $135.79   12.386%   $152.6089   $152.61   $152.60   $152.60  
  7 purchase totals = $1,027.17       $1,123.6594   $1,123.67   $1,123.70   $1,123.60