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 $182.75   13.666%   $207.7246   $207.72   $207.70   $207.70  
  Purchase #2 $61.49   4.120%   $64.0234   $64.02   $64.00   $64.00  
  Purchase #3 $56.54   7.299%   $60.6669   $60.67   $60.65   $60.70  
  Purchase #4 $229.35   3.870%   $238.2258   $238.23   $238.25   $238.20  
  Purchase #5 $237.59   7.387%   $255.1408   $255.14   $255.15   $255.10  
  Purchase #6 $223.50   8.323%   $242.1019   $242.10   $242.10   $242.10  
  Purchase #7 $119.61   12.705%   $134.8065   $134.81   $134.80   $134.80  
  7 purchase totals = $1,110.83       $1,202.6899   $1,202.69   $1,202.65   $1,202.60