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 $24.59   7.802%   $26.5085   $26.51   $26.50   $26.50  
  Purchase #2 $212.42   12.504%   $238.981   $238.98   $239.00   $239.00  
  Purchase #3 $85.71   10.835%   $94.9967   $95.00   $95.00   $95.00  
  Purchase #4 $85.47   8.186%   $92.4666   $92.47   $92.45   $92.50  
  Purchase #5 $118.95   5.274%   $125.2234   $125.22   $125.20   $125.20  
  Purchase #6 $217.54   3.256%   $224.6231   $224.62   $224.60   $224.60  
  Purchase #7 $241.62   12.494%   $271.808   $271.81   $271.80   $271.80  
  7 purchase totals = $986.30       $1,074.6073   $1,074.61   $1,074.55   $1,074.60