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 $218.72   11.862%   $244.6646   $244.66   $244.65   $244.70  
  Purchase #2 $88.83   4.479%   $92.8087   $92.81   $92.80   $92.80  
  Purchase #3 $249.88   5.848%   $264.493   $264.49   $264.50   $264.50  
  Purchase #4 $215.99   3.576%   $223.7138   $223.71   $223.70   $223.70  
  Purchase #5 $184.25   12.235%   $206.793   $206.79   $206.80   $206.80  
  Purchase #6 $145.72   8.741%   $158.4574   $158.46   $158.45   $158.50  
  Purchase #7 $9.56   13.359%   $10.8371   $10.84   $10.85   $10.80  
  7 purchase totals = $1,112.95       $1,201.7676   $1,201.76   $1,201.75   $1,201.80