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 $208.33   11.702%   $232.7088   $232.71   $232.70   $232.70  
  Purchase #2 $224.73   12.491%   $252.801   $252.80   $252.80   $252.80  
  Purchase #3 $77.36   13.411%   $87.7347   $87.73   $87.75   $87.70  
  Purchase #4 $119.71   9.579%   $131.177   $131.18   $131.20   $131.20  
  Purchase #5 $49.34   4.829%   $51.7226   $51.72   $51.70   $51.70  
  Purchase #6 $161.48   12.848%   $182.227   $182.23   $182.25   $182.20  
  Purchase #7 $82.75   6.568%   $88.185   $88.19   $88.20   $88.20  
  7 purchase totals = $923.70       $1,026.5561   $1,026.56   $1,026.60   $1,026.50