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 $49.66   4.662%   $51.9751   $51.98   $52.00   $52.00  
  Purchase #2 $164.54   11.584%   $183.6003   $183.60   $183.60   $183.60  
  Purchase #3 $11.49   8.823%   $12.5038   $12.50   $12.50   $12.50  
  Purchase #4 $242.88   13.335%   $275.268   $275.27   $275.25   $275.30  
  Purchase #5 $193.67   4.299%   $201.9959   $202.00   $202.00   $202.00  
  Purchase #6 $157.85   9.170%   $172.3248   $172.32   $172.30   $172.30  
  Purchase #7 $155.82   13.423%   $176.7357   $176.74   $176.75   $176.70  
  7 purchase totals = $975.91       $1,074.4036   $1,074.41   $1,074.40   $1,074.40