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 $224.69   5.730%   $237.5647   $237.56   $237.55   $237.60  
  Purchase #2 $243.88   4.333%   $254.4473   $254.45   $254.45   $254.40  
  Purchase #3 $15.92   3.281%   $16.4423   $16.44   $16.45   $16.40  
  Purchase #4 $62.44   3.345%   $64.5286   $64.53   $64.55   $64.50  
  Purchase #5 $232.57   11.634%   $259.6272   $259.63   $259.65   $259.60  
  Purchase #6 $208.76   8.629%   $226.7739   $226.77   $226.75   $226.80  
  Purchase #7 $231.51   11.625%   $258.423   $258.42   $258.40   $258.40  
  7 purchase totals = $1,219.77       $1,317.8070   $1,317.80   $1,317.80   $1,317.70