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 $57.39   8.462%   $62.2463   $62.25   $62.25   $62.20  
  Purchase #2 $110.69   13.514%   $125.6486   $125.65   $125.65   $125.60  
  Purchase #3 $237.88   3.832%   $246.9956   $247.00   $247.00   $247.00  
  Purchase #4 $192.55   6.592%   $205.2429   $205.24   $205.25   $205.20  
  Purchase #5 $60.95   4.266%   $63.5501   $63.55   $63.55   $63.60  
  Purchase #6 $128.61   4.151%   $133.9486   $133.95   $133.95   $133.90  
  Purchase #7 $24.28   10.793%   $26.9005   $26.90   $26.90   $26.90  
  7 purchase totals = $812.35       $864.5326   $864.54   $864.55   $864.40