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 $218.71   7.567%   $235.2598   $235.26   $235.25   $235.30  
  Purchase #2 $174.69   9.408%   $191.1248   $191.12   $191.10   $191.10  
  Purchase #3 $62.63   6.607%   $66.768   $66.77   $66.75   $66.80  
  Purchase #4 $83.49   12.253%   $93.72   $93.72   $93.70   $93.70  
  Purchase #5 $65.76   3.573%   $68.1096   $68.11   $68.10   $68.10  
  Purchase #6 $9.32   11.803%   $10.42   $10.42   $10.40   $10.40  
  Purchase #7 $229.76   5.492%   $242.3784   $242.38   $242.40   $242.40  
  7 purchase totals = $844.36       $907.7806   $907.78   $907.70   $907.80