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 $235.49   11.278%   $262.0486   $262.05   $262.05   $262.00  
  Purchase #2 $226.56   13.757%   $257.7279   $257.73   $257.75   $257.70  
  Purchase #3 $214.51   12.416%   $241.1436   $241.14   $241.15   $241.10  
  Purchase #4 $210.59   8.822%   $229.1682   $229.17   $229.15   $229.20  
  Purchase #5 $90.55   3.765%   $93.9592   $93.96   $93.95   $94.00  
  Purchase #6 $110.48   3.802%   $114.6804   $114.68   $114.70   $114.70  
  Purchase #7 $120.73   4.623%   $126.3113   $126.31   $126.30   $126.30  
  7 purchase totals = $1,208.91       $1,325.0392   $1,325.04   $1,325.05   $1,325.00