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 $197.93   4.609%   $207.0526   $207.05   $207.05   $207.10  
  Purchase #2 $55.48   3.758%   $57.5649   $57.56   $57.55   $57.60  
  Purchase #3 $61.54   4.315%   $64.1955   $64.20   $64.20   $64.20  
  Purchase #4 $193.46   7.536%   $208.0391   $208.04   $208.05   $208.00  
  Purchase #5 $228.33   6.348%   $242.8244   $242.82   $242.80   $242.80  
  Purchase #6 $52.25   3.726%   $54.1968   $54.20   $54.20   $54.20  
  Purchase #7 $175.26   3.236%   $180.9314   $180.93   $180.95   $180.90  
  7 purchase totals = $964.25       $1,014.8047   $1,014.80   $1,014.80   $1,014.80