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 $207.87   5.162%   $218.6002   $218.60   $218.60   $218.60  
  Purchase #2 $185.25   6.750%   $197.7544   $197.75   $197.75   $197.80  
  Purchase #3 $164.36   5.344%   $173.1434   $173.14   $173.15   $173.10  
  Purchase #4 $248.81   12.721%   $280.4611   $280.46   $280.45   $280.50  
  Purchase #5 $106.65   3.411%   $110.2878   $110.29   $110.30   $110.30  
  Purchase #6 $115.89   3.329%   $119.748   $119.75   $119.75   $119.70  
  Purchase #7 $62.34   11.584%   $69.5615   $69.56   $69.55   $69.60  
  7 purchase totals = $1,091.17       $1,169.5564   $1,169.55   $1,169.55   $1,169.60