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 $58.94   7.665%   $63.4578   $63.46   $63.45   $63.50  
  Purchase #2 $223.53   6.354%   $237.7331   $237.73   $237.75   $237.70  
  Purchase #3 $210.81   4.423%   $220.1341   $220.13   $220.15   $220.10  
  Purchase #4 $32.71   11.272%   $36.3971   $36.40   $36.40   $36.40  
  Purchase #5 $178.25   13.308%   $201.9715   $201.97   $201.95   $202.00  
  Purchase #6 $208.67   7.574%   $224.4747   $224.47   $224.45   $224.50  
  Purchase #7 $115.70   4.431%   $120.8267   $120.83   $120.85   $120.80  
  7 purchase totals = $1,028.61       $1,104.9950   $1,104.99   $1,105.00   $1,105.00