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 $110.96   3.272%   $114.5906   $114.59   $114.60   $114.60  
  Purchase #2 $52.26   12.335%   $58.7063   $58.71   $58.70   $58.70  
  Purchase #3 $206.41   12.816%   $232.8635   $232.86   $232.85   $232.90  
  Purchase #4 $92.42   4.796%   $96.8525   $96.85   $96.85   $96.90  
  Purchase #5 $225.61   12.605%   $254.0481   $254.05   $254.05   $254.00  
  Purchase #6 $214.48   11.735%   $239.6492   $239.65   $239.65   $239.60  
  Purchase #7 $158.55   7.415%   $170.3065   $170.31   $170.30   $170.30  
  7 purchase totals = $1,060.69       $1,167.0167   $1,167.02   $1,167.00   $1,167.00