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 $208.74   7.468%   $224.3287   $224.33   $224.35   $224.30  
  Purchase #2 $221.84   3.432%   $229.4535   $229.45   $229.45   $229.50  
  Purchase #3 $216.65   3.436%   $224.0941   $224.09   $224.10   $224.10  
  Purchase #4 $148.72   5.202%   $156.4564   $156.46   $156.45   $156.50  
  Purchase #5 $166.32   5.431%   $175.3528   $175.35   $175.35   $175.40  
  Purchase #6 $197.59   10.645%   $218.6235   $218.62   $218.60   $218.60  
  Purchase #7 $38.44   5.731%   $40.643   $40.64   $40.65   $40.60  
  7 purchase totals = $1,198.30       $1,268.9520   $1,268.94   $1,268.95   $1,269.00