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 $188.41   3.668%   $195.3209   $195.32   $195.30   $195.30  
  Purchase #2 $250.87   4.403%   $261.9158   $261.92   $261.90   $261.90  
  Purchase #3 $217.60   6.835%   $232.473   $232.47   $232.45   $232.50  
  Purchase #4 $63.51   11.859%   $71.0417   $71.04   $71.05   $71.00  
  Purchase #5 $78.81   3.841%   $81.8371   $81.84   $81.85   $81.80  
  Purchase #6 $186.57   11.517%   $208.0573   $208.06   $208.05   $208.10  
  Purchase #7 $40.85   10.268%   $45.0445   $45.04   $45.05   $45.00  
  7 purchase totals = $1,026.62       $1,095.6903   $1,095.69   $1,095.65   $1,095.60