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 $61.84   9.571%   $67.7587   $67.76   $67.75   $67.80  
  Purchase #2 $106.45   12.631%   $119.8957   $119.90   $119.90   $119.90  
  Purchase #3 $69.62   5.398%   $73.3781   $73.38   $73.40   $73.40  
  Purchase #4 $229.36   12.652%   $258.3786   $258.38   $258.40   $258.40  
  Purchase #5 $211.93   9.854%   $232.8136   $232.81   $232.80   $232.80  
  Purchase #6 $152.64   6.835%   $163.0729   $163.07   $163.05   $163.10  
  Purchase #7 $199.77   6.693%   $213.1406   $213.14   $213.15   $213.10  
  7 purchase totals = $1,031.61       $1,128.4382   $1,128.44   $1,128.45   $1,128.50