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 $201.68   3.407%   $208.5512   $208.55   $208.55   $208.60  
  Purchase #2 $65.70   6.462%   $69.9455   $69.95   $69.95   $69.90  
  Purchase #3 $244.62   4.233%   $254.9748   $254.97   $254.95   $255.00  
  Purchase #4 $174.87   3.300%   $180.6407   $180.64   $180.65   $180.60  
  Purchase #5 $178.41   12.753%   $201.1626   $201.16   $201.15   $201.20  
  Purchase #6 $242.53   8.288%   $262.6309   $262.63   $262.65   $262.60  
  Purchase #7 $193.80   11.402%   $215.8971   $215.90   $215.90   $215.90  
  7 purchase totals = $1,301.61       $1,393.8028   $1,393.80   $1,393.80   $1,393.80