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 $191.93   4.868%   $201.2732   $201.27   $201.25   $201.30  
  Purchase #2 $21.97   5.196%   $23.1116   $23.11   $23.10   $23.10  
  Purchase #3 $38.41   8.380%   $41.6288   $41.63   $41.65   $41.60  
  Purchase #4 $45.46   8.589%   $49.3646   $49.36   $49.35   $49.40  
  Purchase #5 $138.38   13.314%   $156.8039   $156.80   $156.80   $156.80  
  Purchase #6 $181.83   9.197%   $198.5529   $198.55   $198.55   $198.60  
  Purchase #7 $27.30   6.835%   $29.166   $29.17   $29.15   $29.20  
  7 purchase totals = $645.28       $699.9010   $699.89   $699.85   $700.00