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 $184.49   9.595%   $202.1918   $202.19   $202.20   $202.20  
  Purchase #2 $186.94   10.203%   $206.0135   $206.01   $206.00   $206.00  
  Purchase #3 $67.55   9.616%   $74.0456   $74.05   $74.05   $74.00  
  Purchase #4 $249.78   9.455%   $273.3967   $273.40   $273.40   $273.40  
  Purchase #5 $174.61   12.372%   $196.2127   $196.21   $196.20   $196.20  
  Purchase #6 $153.91   5.461%   $162.315   $162.32   $162.30   $162.30  
  Purchase #7 $208.42   7.336%   $223.7097   $223.71   $223.70   $223.70  
  7 purchase totals = $1,225.70       $1,337.8850   $1,337.89   $1,337.85   $1,337.80