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 $32.53   9.433%   $35.5986   $35.60   $35.60   $35.60  
  Purchase #2 $97.34   12.652%   $109.6555   $109.66   $109.65   $109.70  
  Purchase #3 $212.31   8.130%   $229.5708   $229.57   $229.55   $229.60  
  Purchase #4 $181.25   9.451%   $198.3799   $198.38   $198.40   $198.40  
  Purchase #5 $139.42   10.503%   $154.0633   $154.06   $154.05   $154.10  
  Purchase #6 $240.74   7.714%   $259.3107   $259.31   $259.30   $259.30  
  Purchase #7 $134.36   10.351%   $148.2676   $148.27   $148.25   $148.30  
  7 purchase totals = $1,037.95       $1,134.8464   $1,134.85   $1,134.80   $1,135.00