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 $191.94   11.778%   $214.5467   $214.55   $214.55   $214.50  
  Purchase #2 $247.44   5.681%   $261.4971   $261.50   $261.50   $261.50  
  Purchase #3 $187.34   7.323%   $201.0589   $201.06   $201.05   $201.10  
  Purchase #4 $68.29   5.755%   $72.2201   $72.22   $72.20   $72.20  
  Purchase #5 $249.51   3.529%   $258.3152   $258.32   $258.30   $258.30  
  Purchase #6 $5.76   8.169%   $6.2305   $6.23   $6.25   $6.20  
  Purchase #7 $173.53   13.407%   $196.7952   $196.80   $196.80   $196.80  
  7 purchase totals = $1,123.81       $1,210.6637   $1,210.68   $1,210.65   $1,210.60