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 $146.46   10.618%   $162.0111   $162.01   $162.00   $162.00  
  Purchase #2 $126.55   7.778%   $136.3931   $136.39   $136.40   $136.40  
  Purchase #3 $156.97   10.622%   $173.6434   $173.64   $173.65   $173.60  
  Purchase #4 $198.60   3.816%   $206.1786   $206.18   $206.20   $206.20  
  Purchase #5 $250.44   9.238%   $273.5756   $273.58   $273.60   $273.60  
  Purchase #6 $68.89   10.357%   $76.0249   $76.02   $76.00   $76.00  
  Purchase #7 $74.87   10.849%   $82.9926   $82.99   $83.00   $83.00  
  7 purchase totals = $1,022.78       $1,110.8193   $1,110.81   $1,110.85   $1,110.80