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 $119.68   9.218%   $130.7121   $130.71   $130.70   $130.70  
  Purchase #2 $77.79   11.684%   $86.879   $86.88   $86.90   $86.90  
  Purchase #3 $26.80   6.354%   $28.5029   $28.50   $28.50   $28.50  
  Purchase #4 $5.74   8.746%   $6.242   $6.24   $6.25   $6.20  
  Purchase #5 $209.80   11.681%   $234.3067   $234.31   $234.30   $234.30  
  Purchase #6 $20.41   12.686%   $22.9992   $23.00   $23.00   $23.00  
  Purchase #7 $236.44   4.296%   $246.5975   $246.60   $246.60   $246.60  
  7 purchase totals = $696.66       $756.2394   $756.24   $756.25   $756.20