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 $232.89   12.196%   $261.2933   $261.29   $261.30   $261.30  
  Purchase #2 $54.81   13.844%   $62.3979   $62.40   $62.40   $62.40  
  Purchase #3 $248.44   11.373%   $276.6951   $276.70   $276.70   $276.70  
  Purchase #4 $237.27   11.301%   $264.0839   $264.08   $264.10   $264.10  
  Purchase #5 $59.40   3.760%   $61.6334   $61.63   $61.65   $61.60  
  Purchase #6 $14.57   11.833%   $16.2941   $16.29   $16.30   $16.30  
  Purchase #7 $230.31   13.850%   $262.2079   $262.21   $262.20   $262.20  
  7 purchase totals = $1,077.69       $1,204.6056   $1,204.60   $1,204.65   $1,204.60