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 $60.68   11.415%   $67.6066   $67.61   $67.60   $67.60  
  Purchase #2 $126.72   5.394%   $133.5553   $133.56   $133.55   $133.60  
  Purchase #3 $151.47   6.712%   $161.6367   $161.64   $161.65   $161.60  
  Purchase #4 $158.79   10.514%   $175.4852   $175.49   $175.50   $175.50  
  Purchase #5 $71.54   6.772%   $76.3847   $76.38   $76.40   $76.40  
  Purchase #6 $98.70   5.624%   $104.2509   $104.25   $104.25   $104.30  
  Purchase #7 $53.64   4.576%   $56.0946   $56.09   $56.10   $56.10  
  7 purchase totals = $721.54       $775.0140   $775.02   $775.05   $775.10