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 $87.68   8.544%   $95.1714   $95.17   $95.15   $95.20  
  Purchase #2 $202.92   11.330%   $225.9108   $225.91   $225.90   $225.90  
  Purchase #3 $90.63   5.287%   $95.4216   $95.42   $95.40   $95.40  
  Purchase #4 $210.25   9.126%   $229.4374   $229.44   $229.45   $229.40  
  Purchase #5 $119.32   13.224%   $135.0989   $135.10   $135.10   $135.10  
  Purchase #6 $13.93   12.501%   $15.6714   $15.67   $15.65   $15.70  
  Purchase #7 $197.33   8.706%   $214.5095   $214.51   $214.50   $214.50  
  7 purchase totals = $922.06       $1,011.2210   $1,011.22   $1,011.15   $1,011.20