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 $72.90   5.866%   $77.1763   $77.18   $77.20   $77.20  
  Purchase #2 $208.54   12.380%   $234.3573   $234.36   $234.35   $234.40  
  Purchase #3 $232.82   4.190%   $242.5752   $242.58   $242.60   $242.60  
  Purchase #4 $198.99   4.228%   $207.4033   $207.40   $207.40   $207.40  
  Purchase #5 $100.29   7.323%   $107.6342   $107.63   $107.65   $107.60  
  Purchase #6 $102.37   12.177%   $114.8356   $114.84   $114.85   $114.80  
  Purchase #7 $10.86   4.255%   $11.3221   $11.32   $11.30   $11.30  
  7 purchase totals = $926.77       $995.3040   $995.31   $995.35   $995.30