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 $232.77   5.662%   $245.9494   $245.95   $245.95   $245.90  
  Purchase #2 $196.28   8.719%   $213.3937   $213.39   $213.40   $213.40  
  Purchase #3 $51.91   7.393%   $55.7477   $55.75   $55.75   $55.70  
  Purchase #4 $196.62   5.828%   $208.079   $208.08   $208.10   $208.10  
  Purchase #5 $144.54   13.529%   $164.0948   $164.09   $164.10   $164.10  
  Purchase #6 $128.85   13.194%   $145.8505   $145.85   $145.85   $145.90  
  Purchase #7 $70.84   7.243%   $75.9709   $75.97   $75.95   $76.00  
  7 purchase totals = $1,021.81       $1,109.0860   $1,109.08   $1,109.10   $1,109.10