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 $208.66   13.366%   $236.5495   $236.55   $236.55   $236.50  
  Purchase #2 $132.59   12.182%   $148.7421   $148.74   $148.75   $148.70  
  Purchase #3 $202.59   11.449%   $225.7845   $225.78   $225.80   $225.80  
  Purchase #4 $54.45   12.318%   $61.1572   $61.16   $61.15   $61.20  
  Purchase #5 $50.58   11.122%   $56.2055   $56.21   $56.20   $56.20  
  Purchase #6 $171.67   6.525%   $182.8715   $182.87   $182.85   $182.90  
  Purchase #7 $233.69   7.260%   $250.6559   $250.66   $250.65   $250.70  
  7 purchase totals = $1,054.23       $1,161.9662   $1,161.97   $1,161.95   $1,162.00