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 $82.77   13.611%   $94.0358   $94.04   $94.05   $94.00  
  Purchase #2 $161.93   6.766%   $172.8862   $172.89   $172.90   $172.90  
  Purchase #3 $108.75   12.818%   $122.6896   $122.69   $122.70   $122.70  
  Purchase #4 $191.81   5.386%   $202.1409   $202.14   $202.15   $202.10  
  Purchase #5 $122.28   10.334%   $134.9164   $134.92   $134.90   $134.90  
  Purchase #6 $189.86   8.436%   $205.8766   $205.88   $205.90   $205.90  
  Purchase #7 $9.36   11.821%   $10.4664   $10.47   $10.45   $10.50  
  7 purchase totals = $866.76       $943.0119   $943.03   $943.05   $943.00