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 $201.95   11.725%   $225.6286   $225.63   $225.65   $225.60  
  Purchase #2 $140.94   5.323%   $148.4422   $148.44   $148.45   $148.40  
  Purchase #3 $177.96   13.216%   $201.4792   $201.48   $201.50   $201.50  
  Purchase #4 $112.35   10.595%   $124.2535   $124.25   $124.25   $124.30  
  Purchase #5 $24.92   7.817%   $26.868   $26.87   $26.85   $26.90  
  Purchase #6 $194.54   6.776%   $207.722   $207.72   $207.70   $207.70  
  Purchase #7 $203.29   11.783%   $227.2437   $227.24   $227.25   $227.20  
  7 purchase totals = $1,055.95       $1,161.6372   $1,161.63   $1,161.65   $1,161.60