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 $83.57   12.869%   $94.3246   $94.32   $94.30   $94.30  
  Purchase #2 $101.71   8.870%   $110.7317   $110.73   $110.75   $110.70  
  Purchase #3 $242.92   7.845%   $261.9771   $261.98   $262.00   $262.00  
  Purchase #4 $94.99   13.476%   $107.7909   $107.79   $107.80   $107.80  
  Purchase #5 $150.43   3.631%   $155.8921   $155.89   $155.90   $155.90  
  Purchase #6 $144.31   13.294%   $163.4946   $163.49   $163.50   $163.50  
  Purchase #7 $192.54   13.446%   $218.4289   $218.43   $218.45   $218.40  
  7 purchase totals = $1,010.47       $1,112.6399   $1,112.63   $1,112.70   $1,112.60