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 $222.80   7.565%   $239.6548   $239.65   $239.65   $239.70  
  Purchase #2 $249.88   7.609%   $268.8934   $268.89   $268.90   $268.90  
  Purchase #3 $83.59   10.209%   $92.1237   $92.12   $92.10   $92.10  
  Purchase #4 $24.59   11.787%   $27.4884   $27.49   $27.50   $27.50  
  Purchase #5 $250.97   5.849%   $265.6492   $265.65   $265.65   $265.60  
  Purchase #6 $173.58   7.322%   $186.2895   $186.29   $186.30   $186.30  
  Purchase #7 $42.42   10.856%   $47.0251   $47.03   $47.05   $47.00  
  7 purchase totals = $1,047.83       $1,127.1241   $1,127.12   $1,127.15   $1,127.10