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 $65.83   11.169%   $73.1826   $73.18   $73.20   $73.20  
  Purchase #2 $198.69   10.372%   $219.2981   $219.30   $219.30   $219.30  
  Purchase #3 $58.26   12.729%   $65.6759   $65.68   $65.70   $65.70  
  Purchase #4 $92.61   7.219%   $99.2955   $99.30   $99.30   $99.30  
  Purchase #5 $234.72   11.598%   $261.9428   $261.94   $261.95   $261.90  
  Purchase #6 $80.67   5.257%   $84.9108   $84.91   $84.90   $84.90  
  Purchase #7 $186.87   10.836%   $207.1192   $207.12   $207.10   $207.10  
  7 purchase totals = $917.65       $1,011.4249   $1,011.43   $1,011.45   $1,011.40