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 $60.61   3.213%   $62.5574   $62.56   $62.55   $62.60  
  Purchase #2 $154.44   7.605%   $166.1852   $166.19   $166.20   $166.20  
  Purchase #3 $241.59   8.611%   $262.3933   $262.39   $262.40   $262.40  
  Purchase #4 $73.99   11.458%   $82.4678   $82.47   $82.45   $82.50  
  Purchase #5 $75.62   5.827%   $80.0264   $80.03   $80.05   $80.00  
  Purchase #6 $236.76   4.625%   $247.7102   $247.71   $247.70   $247.70  
  Purchase #7 $158.74   4.775%   $166.3198   $166.32   $166.30   $166.30  
  7 purchase totals = $1,001.75       $1,067.6601   $1,067.67   $1,067.65   $1,067.70