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 $88.94   7.544%   $95.6496   $95.65   $95.65   $95.60  
  Purchase #2 $122.64   8.588%   $133.1723   $133.17   $133.15   $133.20  
  Purchase #3 $209.85   3.346%   $216.8716   $216.87   $216.85   $216.90  
  Purchase #4 $148.42   12.328%   $166.7172   $166.72   $166.70   $166.70  
  Purchase #5 $23.99   9.731%   $26.3245   $26.32   $26.30   $26.30  
  Purchase #6 $163.51   9.818%   $179.5634   $179.56   $179.55   $179.60  
  Purchase #7 $132.42   6.837%   $141.4736   $141.47   $141.45   $141.50  
  7 purchase totals = $889.77       $959.7722   $959.76   $959.65   $959.80