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 $60.43   3.767%   $62.7064   $62.71   $62.70   $62.70  
  Purchase #2 $189.81   3.349%   $196.1667   $196.17   $196.15   $196.20  
  Purchase #3 $36.90   3.508%   $38.1945   $38.19   $38.20   $38.20  
  Purchase #4 $198.77   4.637%   $207.987   $207.99   $208.00   $208.00  
  Purchase #5 $188.53   13.418%   $213.827   $213.83   $213.85   $213.80  
  Purchase #6 $146.70   10.589%   $162.2341   $162.23   $162.25   $162.20  
  Purchase #7 $137.88   11.490%   $153.7224   $153.72   $153.70   $153.70  
  7 purchase totals = $959.02       $1,034.8381   $1,034.84   $1,034.85   $1,034.80