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 $213.76   13.679%   $243.0002   $243.00   $243.00   $243.00  
  Purchase #2 $33.73   3.608%   $34.947   $34.95   $34.95   $34.90  
  Purchase #3 $58.49   3.706%   $60.6576   $60.66   $60.65   $60.70  
  Purchase #4 $226.62   12.710%   $255.4234   $255.42   $255.40   $255.40  
  Purchase #5 $179.81   12.834%   $202.8868   $202.89   $202.90   $202.90  
  Purchase #6 $174.76   9.372%   $191.1385   $191.14   $191.15   $191.10  
  Purchase #7 $54.69   9.682%   $59.9851   $59.99   $60.00   $60.00  
  7 purchase totals = $941.86       $1,048.0386   $1,048.05   $1,048.05   $1,048.00