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 $181.25   8.418%   $196.5076   $196.51   $196.50   $196.50  
  Purchase #2 $179.50   12.114%   $201.2446   $201.24   $201.25   $201.20  
  Purchase #3 $182.29   10.867%   $202.0995   $202.10   $202.10   $202.10  
  Purchase #4 $41.79   5.565%   $44.1156   $44.12   $44.10   $44.10  
  Purchase #5 $156.83   10.714%   $173.6328   $173.63   $173.65   $173.60  
  Purchase #6 $21.81   6.786%   $23.29   $23.29   $23.30   $23.30  
  Purchase #7 $12.55   13.185%   $14.2047   $14.20   $14.20   $14.20  
  7 purchase totals = $776.02       $855.0948   $855.09   $855.10   $855.00