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 $108.39   5.419%   $114.2637   $114.26   $114.25   $114.30  
  Purchase #2 $223.60   12.575%   $251.7177   $251.72   $251.70   $251.70  
  Purchase #3 $50.51   11.326%   $56.2308   $56.23   $56.25   $56.20  
  Purchase #4 $122.94   13.141%   $139.0955   $139.10   $139.10   $139.10  
  Purchase #5 $211.91   12.385%   $238.1551   $238.16   $238.15   $238.20  
  Purchase #6 $109.39   6.192%   $116.1634   $116.16   $116.15   $116.20  
  Purchase #7 $210.79   12.216%   $236.5401   $236.54   $236.55   $236.50  
  7 purchase totals = $1,037.53       $1,152.1663   $1,152.17   $1,152.15   $1,152.20