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 $113.32   5.113%   $119.1141   $119.11   $119.10   $119.10  
  Purchase #2 $57.36   10.605%   $63.443   $63.44   $63.45   $63.40  
  Purchase #3 $67.66   9.351%   $73.9869   $73.99   $74.00   $74.00  
  Purchase #4 $235.53   5.654%   $248.8469   $248.85   $248.85   $248.80  
  Purchase #5 $164.73   4.410%   $171.9946   $171.99   $172.00   $172.00  
  Purchase #6 $243.28   5.838%   $257.4827   $257.48   $257.50   $257.50  
  Purchase #7 $25.73   13.669%   $29.247   $29.25   $29.25   $29.20  
  7 purchase totals = $907.61       $964.1152   $964.11   $964.15   $964.00