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 $191.75   5.482%   $202.2617   $202.26   $202.25   $202.30  
  Purchase #2 $63.72   3.847%   $66.1713   $66.17   $66.15   $66.20  
  Purchase #3 $27.32   4.741%   $28.6152   $28.62   $28.60   $28.60  
  Purchase #4 $200.78   5.390%   $211.602   $211.60   $211.60   $211.60  
  Purchase #5 $197.83   5.379%   $208.4713   $208.47   $208.45   $208.50  
  Purchase #6 $115.53   4.225%   $120.4111   $120.41   $120.40   $120.40  
  Purchase #7 $186.36   6.287%   $198.0765   $198.08   $198.10   $198.10  
  7 purchase totals = $983.29       $1,035.6091   $1,035.61   $1,035.55   $1,035.70