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 $222.72   8.634%   $241.9496   $241.95   $241.95   $241.90  
  Purchase #2 $232.86   5.450%   $245.5509   $245.55   $245.55   $245.60  
  Purchase #3 $21.79   9.448%   $23.8487   $23.85   $23.85   $23.80  
  Purchase #4 $248.85   11.412%   $277.2488   $277.25   $277.25   $277.20  
  Purchase #5 $45.72   8.481%   $49.5975   $49.60   $49.60   $49.60  
  Purchase #6 $229.56   8.533%   $249.1484   $249.15   $249.15   $249.10  
  Purchase #7 $197.59   5.547%   $208.5503   $208.55   $208.55   $208.60  
  7 purchase totals = $1,199.09       $1,295.8942   $1,295.90   $1,295.90   $1,295.80