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 $59.63   6.703%   $63.627   $63.63   $63.65   $63.60  
  Purchase #2 $178.84   4.175%   $186.3066   $186.31   $186.30   $186.30  
  Purchase #3 $157.46   12.204%   $176.6764   $176.68   $176.70   $176.70  
  Purchase #4 $78.66   8.123%   $85.0496   $85.05   $85.05   $85.00  
  Purchase #5 $212.64   13.676%   $241.7206   $241.72   $241.70   $241.70  
  Purchase #6 $249.62   6.872%   $266.7739   $266.77   $266.75   $266.80  
  Purchase #7 $230.50   10.681%   $255.1197   $255.12   $255.10   $255.10  
  7 purchase totals = $1,167.35       $1,275.2738   $1,275.28   $1,275.25   $1,275.20