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 $211.91   10.316%   $233.7706   $233.77   $233.75   $233.80  
  Purchase #2 $188.59   11.689%   $210.6343   $210.63   $210.65   $210.60  
  Purchase #3 $174.92   4.455%   $182.7127   $182.71   $182.70   $182.70  
  Purchase #4 $140.88   11.587%   $157.2038   $157.20   $157.20   $157.20  
  Purchase #5 $156.48   6.593%   $166.7967   $166.80   $166.80   $166.80  
  Purchase #6 $107.38   7.163%   $115.0716   $115.07   $115.05   $115.10  
  Purchase #7 $7.79   13.849%   $8.8688   $8.87   $8.85   $8.90  
  7 purchase totals = $987.95       $1,075.0585   $1,075.05   $1,075.00   $1,075.10