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 $213.41   7.373%   $229.1447   $229.14   $229.15   $229.10  
  Purchase #2 $23.74   11.354%   $26.4354   $26.44   $26.45   $26.40  
  Purchase #3 $59.56   11.462%   $66.3868   $66.39   $66.40   $66.40  
  Purchase #4 $157.43   4.732%   $164.8796   $164.88   $164.90   $164.90  
  Purchase #5 $232.40   13.694%   $264.2249   $264.22   $264.20   $264.20  
  Purchase #6 $202.93   5.335%   $213.7563   $213.76   $213.75   $213.80  
  Purchase #7 $92.75   12.313%   $104.1703   $104.17   $104.15   $104.20  
  7 purchase totals = $982.22       $1,068.9980   $1,069.00   $1,069.00   $1,069.00