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 $217.26   8.450%   $235.6185   $235.62   $235.60   $235.60  
  Purchase #2 $97.73   8.129%   $105.6745   $105.67   $105.65   $105.70  
  Purchase #3 $223.29   5.202%   $234.9055   $234.91   $234.90   $234.90  
  Purchase #4 $121.57   3.264%   $125.538   $125.54   $125.55   $125.50  
  Purchase #5 $61.86   4.683%   $64.7569   $64.76   $64.75   $64.80  
  Purchase #6 $186.88   6.210%   $198.4852   $198.49   $198.50   $198.50  
  Purchase #7 $83.57   12.525%   $94.0371   $94.04   $94.05   $94.00  
  7 purchase totals = $992.16       $1,059.0157   $1,059.03   $1,059.00   $1,059.00