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 $60.88   4.419%   $63.5703   $63.57   $63.55   $63.60  
  Purchase #2 $143.93   9.339%   $157.3716   $157.37   $157.35   $157.40  
  Purchase #3 $70.25   11.862%   $78.5831   $78.58   $78.60   $78.60  
  Purchase #4 $149.47   3.391%   $154.5385   $154.54   $154.55   $154.50  
  Purchase #5 $141.74   6.807%   $151.3882   $151.39   $151.40   $151.40  
  Purchase #6 $245.71   10.844%   $272.3548   $272.35   $272.35   $272.40  
  Purchase #7 $214.40   4.645%   $224.3589   $224.36   $224.35   $224.40  
  7 purchase totals = $1,026.38       $1,102.1654   $1,102.16   $1,102.15   $1,102.30