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 $195.77   5.122%   $205.7973   $205.80   $205.80   $205.80  
  Purchase #2 $90.38   9.713%   $99.1586   $99.16   $99.15   $99.20  
  Purchase #3 $151.99   13.745%   $172.881   $172.88   $172.90   $172.90  
  Purchase #4 $226.50   4.393%   $236.4501   $236.45   $236.45   $236.50  
  Purchase #5 $14.70   11.615%   $16.4074   $16.41   $16.40   $16.40  
  Purchase #6 $77.97   5.507%   $82.2638   $82.26   $82.25   $82.30  
  Purchase #7 $68.63   3.277%   $70.879   $70.88   $70.90   $70.90  
  7 purchase totals = $825.94       $883.8372   $883.84   $883.85   $884.00