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 $136.45   4.752%   $142.9341   $142.93   $142.95   $142.90  
  Purchase #2 $161.91   13.853%   $184.3394   $184.34   $184.35   $184.30  
  Purchase #3 $163.28   6.629%   $174.1038   $174.10   $174.10   $174.10  
  Purchase #4 $130.72   10.210%   $144.0665   $144.07   $144.05   $144.10  
  Purchase #5 $114.33   11.226%   $127.1647   $127.16   $127.15   $127.20  
  Purchase #6 $71.88   6.238%   $76.3639   $76.36   $76.35   $76.40  
  Purchase #7 $203.61   5.455%   $214.7169   $214.72   $214.70   $214.70  
  7 purchase totals = $982.18       $1,063.6893   $1,063.68   $1,063.65   $1,063.70