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 $197.58   8.567%   $214.5067   $214.51   $214.50   $214.50  
  Purchase #2 $228.49   8.409%   $247.7037   $247.70   $247.70   $247.70  
  Purchase #3 $107.74   3.708%   $111.735   $111.74   $111.75   $111.70  
  Purchase #4 $168.45   6.682%   $179.7058   $179.71   $179.70   $179.70  
  Purchase #5 $57.88   6.189%   $61.4622   $61.46   $61.45   $61.50  
  Purchase #6 $52.33   7.860%   $56.4431   $56.44   $56.45   $56.40  
  Purchase #7 $23.57   8.249%   $25.5143   $25.51   $25.50   $25.50  
  7 purchase totals = $836.04       $897.0708   $897.07   $897.05   $897.00