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 $196.79   5.722%   $208.0503   $208.05   $208.05   $208.10  
  Purchase #2 $153.49   9.368%   $167.8689   $167.87   $167.85   $167.90  
  Purchase #3 $54.94   8.423%   $59.5676   $59.57   $59.55   $59.60  
  Purchase #4 $110.48   8.869%   $120.2785   $120.28   $120.30   $120.30  
  Purchase #5 $177.38   12.553%   $199.6465   $199.65   $199.65   $199.60  
  Purchase #6 $92.75   6.204%   $98.5042   $98.50   $98.50   $98.50  
  Purchase #7 $105.63   7.730%   $113.7952   $113.80   $113.80   $113.80  
  7 purchase totals = $891.46       $967.7112   $967.72   $967.70   $967.80