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 $55.87   7.709%   $60.177   $60.18   $60.20   $60.20  
  Purchase #2 $151.83   8.528%   $164.7781   $164.78   $164.80   $164.80  
  Purchase #3 $16.27   4.198%   $16.953   $16.95   $16.95   $17.00  
  Purchase #4 $168.57   3.452%   $174.389   $174.39   $174.40   $174.40  
  Purchase #5 $196.56   4.853%   $206.0991   $206.10   $206.10   $206.10  
  Purchase #6 $203.25   11.715%   $227.0607   $227.06   $227.05   $227.10  
  Purchase #7 $207.53   5.874%   $219.7203   $219.72   $219.70   $219.70  
  7 purchase totals = $999.88       $1,069.1772   $1,069.18   $1,069.20   $1,069.30