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 $119.29   4.792%   $125.0064   $125.01   $125.00   $125.00  
  Purchase #2 $49.94   9.257%   $54.5629   $54.56   $54.55   $54.60  
  Purchase #3 $206.49   9.479%   $226.0632   $226.06   $226.05   $226.10  
  Purchase #4 $226.42   5.867%   $239.7041   $239.70   $239.70   $239.70  
  Purchase #5 $57.83   7.324%   $62.0655   $62.07   $62.05   $62.10  
  Purchase #6 $171.93   8.442%   $186.4443   $186.44   $186.45   $186.40  
  Purchase #7 $108.88   13.535%   $123.6169   $123.62   $123.60   $123.60  
  7 purchase totals = $940.78       $1,017.4633   $1,017.46   $1,017.40   $1,017.50