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 $230.61   5.159%   $242.5072   $242.51   $242.50   $242.50  
  Purchase #2 $34.95   5.650%   $36.9247   $36.92   $36.90   $36.90  
  Purchase #3 $53.65   3.802%   $55.6898   $55.69   $55.70   $55.70  
  Purchase #4 $175.68   11.450%   $195.7954   $195.80   $195.80   $195.80  
  Purchase #5 $221.51   7.291%   $237.6603   $237.66   $237.65   $237.70  
  Purchase #6 $186.42   5.265%   $196.235   $196.24   $196.25   $196.20  
  Purchase #7 $161.71   9.319%   $176.7798   $176.78   $176.80   $176.80  
  7 purchase totals = $1,064.53       $1,141.5922   $1,141.60   $1,141.60   $1,141.60