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 $83.36   11.486%   $92.9347   $92.93   $92.95   $92.90  
  Purchase #2 $138.26   13.143%   $156.4315   $156.43   $156.45   $156.40  
  Purchase #3 $114.32   11.262%   $127.1947   $127.19   $127.20   $127.20  
  Purchase #4 $162.42   12.230%   $182.284   $182.28   $182.30   $182.30  
  Purchase #5 $61.30   5.677%   $64.78   $64.78   $64.80   $64.80  
  Purchase #6 $109.67   8.200%   $118.6629   $118.66   $118.65   $118.70  
  Purchase #7 $201.87   5.595%   $213.1646   $213.16   $213.15   $213.20  
  7 purchase totals = $871.20       $955.4524   $955.43   $955.50   $955.50