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 $88.40   9.169%   $96.5054   $96.51   $96.50   $96.50  
  Purchase #2 $93.87   10.293%   $103.532   $103.53   $103.55   $103.50  
  Purchase #3 $177.83   8.470%   $192.8922   $192.89   $192.90   $192.90  
  Purchase #4 $129.65   8.865%   $141.1435   $141.14   $141.15   $141.10  
  Purchase #5 $70.47   10.344%   $77.7594   $77.76   $77.75   $77.80  
  Purchase #6 $167.46   12.649%   $188.642   $188.64   $188.65   $188.60  
  Purchase #7 $213.48   5.686%   $225.6185   $225.62   $225.60   $225.60  
  7 purchase totals = $941.16       $1,026.0930   $1,026.09   $1,026.10   $1,026.00