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 $58.89   5.700%   $62.2467   $62.25   $62.25   $62.20  
  Purchase #2 $104.87   9.236%   $114.5558   $114.56   $114.55   $114.60  
  Purchase #3 $230.71   8.303%   $249.8659   $249.87   $249.85   $249.90  
  Purchase #4 $126.71   12.108%   $142.052   $142.05   $142.05   $142.10  
  Purchase #5 $174.81   10.698%   $193.5112   $193.51   $193.50   $193.50  
  Purchase #6 $157.39   7.171%   $168.6764   $168.68   $168.70   $168.70  
  Purchase #7 $103.59   9.704%   $113.6424   $113.64   $113.65   $113.60  
  7 purchase totals = $956.97       $1,044.5504   $1,044.56   $1,044.55   $1,044.60