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 $168.69   4.141%   $175.6755   $175.68   $175.70   $175.70  
  Purchase #2 $250.71   7.617%   $269.8066   $269.81   $269.80   $269.80  
  Purchase #3 $42.30   10.595%   $46.7817   $46.78   $46.80   $46.80  
  Purchase #4 $245.82   11.343%   $273.7034   $273.70   $273.70   $273.70  
  Purchase #5 $241.49   5.394%   $254.516   $254.52   $254.50   $254.50  
  Purchase #6 $17.66   9.742%   $19.3804   $19.38   $19.40   $19.40  
  Purchase #7 $85.27   11.838%   $95.3643   $95.36   $95.35   $95.40  
  7 purchase totals = $1,051.94       $1,135.2279   $1,135.23   $1,135.25   $1,135.30