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 $212.68   9.415%   $232.7038   $232.70   $232.70   $232.70  
  Purchase #2 $34.46   5.759%   $36.4446   $36.44   $36.45   $36.40  
  Purchase #3 $248.53   4.685%   $260.1736   $260.17   $260.15   $260.20  
  Purchase #4 $179.88   3.542%   $186.2513   $186.25   $186.25   $186.30  
  Purchase #5 $96.69   11.286%   $107.6024   $107.60   $107.60   $107.60  
  Purchase #6 $80.88   5.493%   $85.3227   $85.32   $85.30   $85.30  
  Purchase #7 $27.47   3.618%   $28.4639   $28.46   $28.45   $28.50  
  7 purchase totals = $880.59       $936.9623   $936.94   $936.90   $937.00