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 $195.99   5.458%   $206.6871   $206.69   $206.70   $206.70  
  Purchase #2 $240.61   5.212%   $253.1506   $253.15   $253.15   $253.20  
  Purchase #3 $245.82   4.330%   $256.464   $256.46   $256.45   $256.50  
  Purchase #4 $225.79   5.500%   $238.2085   $238.21   $238.20   $238.20  
  Purchase #5 $33.63   7.270%   $36.0749   $36.07   $36.05   $36.10  
  Purchase #6 $5.64   9.340%   $6.1668   $6.17   $6.15   $6.20  
  Purchase #7 $104.31   8.779%   $113.4674   $113.47   $113.45   $113.50  
  7 purchase totals = $1,051.79       $1,110.2193   $1,110.22   $1,110.15   $1,110.40