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 $119.53   5.742%   $126.3934   $126.39   $126.40   $126.40  
  Purchase #2 $10.53   10.691%   $11.6558   $11.66   $11.65   $11.70  
  Purchase #3 $114.93   9.847%   $126.2472   $126.25   $126.25   $126.20  
  Purchase #4 $121.53   11.850%   $135.9313   $135.93   $135.95   $135.90  
  Purchase #5 $212.66   6.685%   $226.8763   $226.88   $226.90   $226.90  
  Purchase #6 $15.77   4.253%   $16.4407   $16.44   $16.45   $16.40  
  Purchase #7 $197.74   5.556%   $208.7264   $208.73   $208.75   $208.70  
  7 purchase totals = $792.69       $852.2711   $852.28   $852.35   $852.20