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 $193.62   11.439%   $215.7682   $215.77   $215.75   $215.80  
  Purchase #2 $239.28   9.723%   $262.5452   $262.55   $262.55   $262.50  
  Purchase #3 $21.30   11.181%   $23.6816   $23.68   $23.70   $23.70  
  Purchase #4 $112.72   11.326%   $125.4867   $125.49   $125.50   $125.50  
  Purchase #5 $246.71   4.838%   $258.6458   $258.65   $258.65   $258.60  
  Purchase #6 $247.47   13.782%   $281.5763   $281.58   $281.60   $281.60  
  Purchase #7 $202.25   5.656%   $213.6893   $213.69   $213.70   $213.70  
  7 purchase totals = $1,263.35       $1,381.3931   $1,381.41   $1,381.45   $1,381.40