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 $232.56   13.214%   $263.2905   $263.29   $263.30   $263.30  
  Purchase #2 $224.65   5.609%   $237.2506   $237.25   $237.25   $237.30  
  Purchase #3 $216.83   8.709%   $235.7137   $235.71   $235.70   $235.70  
  Purchase #4 $31.38   7.664%   $33.785   $33.79   $33.80   $33.80  
  Purchase #5 $233.95   6.682%   $249.5825   $249.58   $249.60   $249.60  
  Purchase #6 $93.71   12.596%   $105.5137   $105.51   $105.50   $105.50  
  Purchase #7 $54.68   4.836%   $57.3243   $57.32   $57.30   $57.30  
  7 purchase totals = $1,087.76       $1,182.4603   $1,182.45   $1,182.45   $1,182.50