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 $59.25   5.872%   $62.7292   $62.73   $62.75   $62.70  
  Purchase #2 $247.57   6.778%   $264.3503   $264.35   $264.35   $264.40  
  Purchase #3 $16.80   13.812%   $19.1204   $19.12   $19.10   $19.10  
  Purchase #4 $72.30   11.406%   $80.5465   $80.55   $80.55   $80.50  
  Purchase #5 $55.39   3.605%   $57.3868   $57.39   $57.40   $57.40  
  Purchase #6 $186.58   11.238%   $207.5479   $207.55   $207.55   $207.50  
  Purchase #7 $103.25   4.522%   $107.919   $107.92   $107.90   $107.90  
  7 purchase totals = $741.14       $799.6001   $799.61   $799.60   $799.50