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 $195.63   5.669%   $206.7203   $206.72   $206.70   $206.70  
  Purchase #2 $164.97   11.715%   $184.2962   $184.30   $184.30   $184.30  
  Purchase #3 $53.99   10.411%   $59.6109   $59.61   $59.60   $59.60  
  Purchase #4 $163.58   8.388%   $177.3011   $177.30   $177.30   $177.30  
  Purchase #5 $250.70   13.295%   $284.0306   $284.03   $284.05   $284.00  
  Purchase #6 $45.77   10.471%   $50.5626   $50.56   $50.55   $50.60  
  Purchase #7 $52.62   5.451%   $55.4883   $55.49   $55.50   $55.50  
  7 purchase totals = $927.26       $1,018.0100   $1,018.01   $1,018.00   $1,018.00