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 $56.49   10.386%   $62.3571   $62.36   $62.35   $62.40  
  Purchase #2 $114.49   9.256%   $125.0872   $125.09   $125.10   $125.10  
  Purchase #3 $183.32   10.180%   $201.982   $201.98   $202.00   $202.00  
  Purchase #4 $44.57   13.451%   $50.5651   $50.57   $50.55   $50.60  
  Purchase #5 $72.35   3.175%   $74.6471   $74.65   $74.65   $74.60  
  Purchase #6 $104.97   6.735%   $112.0397   $112.04   $112.05   $112.00  
  Purchase #7 $218.46   9.711%   $239.6747   $239.67   $239.65   $239.70  
  7 purchase totals = $794.65       $866.3529   $866.36   $866.35   $866.40