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 $86.72   6.490%   $92.3481   $92.35   $92.35   $92.30  
  Purchase #2 $208.92   10.405%   $230.6581   $230.66   $230.65   $230.70  
  Purchase #3 $31.43   12.670%   $35.4122   $35.41   $35.40   $35.40  
  Purchase #4 $224.51   13.622%   $255.0928   $255.09   $255.10   $255.10  
  Purchase #5 $98.39   6.404%   $104.6909   $104.69   $104.70   $104.70  
  Purchase #6 $179.42   8.847%   $195.2933   $195.29   $195.30   $195.30  
  Purchase #7 $94.83   3.521%   $98.169   $98.17   $98.15   $98.20  
  7 purchase totals = $924.22       $1,011.6644   $1,011.66   $1,011.65   $1,011.70