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 $214.39   10.838%   $237.6256   $237.63   $237.65   $237.60  
  Purchase #2 $83.48   4.115%   $86.9152   $86.92   $86.90   $86.90  
  Purchase #3 $201.83   12.657%   $227.3756   $227.38   $227.40   $227.40  
  Purchase #4 $139.33   12.590%   $156.8716   $156.87   $156.85   $156.90  
  Purchase #5 $191.94   4.788%   $201.1301   $201.13   $201.15   $201.10  
  Purchase #6 $152.71   9.135%   $166.6601   $166.66   $166.65   $166.70  
  Purchase #7 $68.96   5.690%   $72.8838   $72.88   $72.90   $72.90  
  7 purchase totals = $1,052.64       $1,149.4620   $1,149.47   $1,149.50   $1,149.50