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 $58.25   11.811%   $65.1299   $65.13   $65.15   $65.10  
  Purchase #2 $82.32   5.383%   $86.7513   $86.75   $86.75   $86.80  
  Purchase #3 $99.77   5.264%   $105.0219   $105.02   $105.00   $105.00  
  Purchase #4 $54.61   13.542%   $62.0053   $62.01   $62.00   $62.00  
  Purchase #5 $208.98   11.435%   $232.8769   $232.88   $232.90   $232.90  
  Purchase #6 $248.75   5.244%   $261.7945   $261.79   $261.80   $261.80  
  Purchase #7 $198.62   6.712%   $211.9514   $211.95   $211.95   $212.00  
  7 purchase totals = $951.30       $1,025.5312   $1,025.53   $1,025.55   $1,025.60