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 $77.38   7.197%   $82.949   $82.95   $82.95   $82.90  
  Purchase #2 $172.64   11.418%   $192.352   $192.35   $192.35   $192.40  
  Purchase #3 $24.91   4.772%   $26.0987   $26.10   $26.10   $26.10  
  Purchase #4 $186.42   6.725%   $198.9567   $198.96   $198.95   $199.00  
  Purchase #5 $248.49   7.802%   $267.8772   $267.88   $267.90   $267.90  
  Purchase #6 $214.28   8.601%   $232.7102   $232.71   $232.70   $232.70  
  Purchase #7 $6.64   4.501%   $6.9389   $6.94   $6.95   $6.90  
  7 purchase totals = $930.76       $1,007.8827   $1,007.89   $1,007.90   $1,007.90