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 $175.99   11.665%   $196.5192   $196.52   $196.50   $196.50  
  Purchase #2 $89.37   5.387%   $94.1844   $94.18   $94.20   $94.20  
  Purchase #3 $197.47   11.177%   $219.5412   $219.54   $219.55   $219.50  
  Purchase #4 $208.79   13.834%   $237.674   $237.67   $237.65   $237.70  
  Purchase #5 $161.38   7.331%   $173.2108   $173.21   $173.20   $173.20  
  Purchase #6 $18.25   5.595%   $19.2711   $19.27   $19.25   $19.30  
  Purchase #7 $13.94   5.662%   $14.7293   $14.73   $14.75   $14.70  
  7 purchase totals = $865.19       $955.1300   $955.12   $955.10   $955.10