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 $197.51   5.571%   $208.5133   $208.51   $208.50   $208.50  
  Purchase #2 $23.44   4.356%   $24.461   $24.46   $24.45   $24.50  
  Purchase #3 $167.82   4.846%   $175.9526   $175.95   $175.95   $176.00  
  Purchase #4 $13.79   4.764%   $14.447   $14.45   $14.45   $14.40  
  Purchase #5 $24.55   13.359%   $27.8296   $27.83   $27.85   $27.80  
  Purchase #6 $192.83   12.390%   $216.7216   $216.72   $216.70   $216.70  
  Purchase #7 $109.72   8.173%   $118.6874   $118.69   $118.70   $118.70  
  7 purchase totals = $729.66       $786.6125   $786.61   $786.60   $786.60