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 $41.25   5.292%   $43.433   $43.43   $43.45   $43.40  
  Purchase #2 $225.99   6.503%   $240.6861   $240.69   $240.70   $240.70  
  Purchase #3 $77.91   5.521%   $82.2114   $82.21   $82.20   $82.20  
  Purchase #4 $91.54   5.494%   $96.5692   $96.57   $96.55   $96.60  
  Purchase #5 $103.89   3.703%   $107.737   $107.74   $107.75   $107.70  
  Purchase #6 $242.43   11.618%   $270.5955   $270.60   $270.60   $270.60  
  Purchase #7 $102.63   13.218%   $116.1956   $116.20   $116.20   $116.20  
  7 purchase totals = $885.64       $957.4278   $957.44   $957.45   $957.40