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 $72.41   5.196%   $76.1724   $76.17   $76.15   $76.20  
  Purchase #2 $190.93   7.736%   $205.7003   $205.70   $205.70   $205.70  
  Purchase #3 $180.65   12.839%   $203.8437   $203.84   $203.85   $203.80  
  Purchase #4 $146.45   12.471%   $164.7138   $164.71   $164.70   $164.70  
  Purchase #5 $222.28   6.448%   $236.6126   $236.61   $236.60   $236.60  
  Purchase #6 $125.61   10.789%   $139.1621   $139.16   $139.15   $139.20  
  Purchase #7 $53.75   4.743%   $56.2994   $56.30   $56.30   $56.30  
  7 purchase totals = $992.08       $1,082.5043   $1,082.49   $1,082.45   $1,082.50