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 $49.93   7.353%   $53.6014   $53.60   $53.60   $53.60  
  Purchase #2 $188.78   4.183%   $196.6767   $196.68   $196.70   $196.70  
  Purchase #3 $23.35   5.573%   $24.6513   $24.65   $24.65   $24.70  
  Purchase #4 $112.58   12.639%   $126.809   $126.81   $126.80   $126.80  
  Purchase #5 $226.59   13.699%   $257.6306   $257.63   $257.65   $257.60  
  Purchase #6 $187.85   10.757%   $208.057   $208.06   $208.05   $208.10  
  Purchase #7 $176.25   10.806%   $195.2956   $195.30   $195.30   $195.30  
  7 purchase totals = $965.33       $1,062.7216   $1,062.73   $1,062.75   $1,062.80