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 $116.89   7.762%   $125.963   $125.96   $125.95   $126.00  
  Purchase #2 $15.89   7.236%   $17.0398   $17.04   $17.05   $17.00  
  Purchase #3 $170.35   7.299%   $182.7838   $182.78   $182.80   $182.80  
  Purchase #4 $172.75   13.584%   $196.2164   $196.22   $196.20   $196.20  
  Purchase #5 $217.64   4.499%   $227.4316   $227.43   $227.45   $227.40  
  Purchase #6 $113.44   12.291%   $127.3829   $127.38   $127.40   $127.40  
  Purchase #7 $207.80   13.511%   $235.8759   $235.88   $235.90   $235.90  
  7 purchase totals = $1,014.76       $1,112.6934   $1,112.69   $1,112.75   $1,112.70