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 $57.52   9.443%   $62.9516   $62.95   $62.95   $63.00  
  Purchase #2 $231.90   7.704%   $249.7656   $249.77   $249.75   $249.80  
  Purchase #3 $241.68   12.127%   $270.9885   $270.99   $271.00   $271.00  
  Purchase #4 $174.89   11.765%   $195.4658   $195.47   $195.45   $195.50  
  Purchase #5 $139.55   4.321%   $145.58   $145.58   $145.60   $145.60  
  Purchase #6 $154.49   6.655%   $164.7713   $164.77   $164.75   $164.80  
  Purchase #7 $161.94   8.312%   $175.4005   $175.40   $175.40   $175.40  
  7 purchase totals = $1,161.97       $1,264.9233   $1,264.93   $1,264.90   $1,265.10