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 $244.89   3.118%   $252.5257   $252.53   $252.55   $252.50  
  Purchase #2 $203.73   6.243%   $216.4489   $216.45   $216.45   $216.40  
  Purchase #3 $68.81   5.116%   $72.3303   $72.33   $72.35   $72.30  
  Purchase #4 $231.76   4.296%   $241.7164   $241.72   $241.70   $241.70  
  Purchase #5 $220.97   13.493%   $250.7855   $250.79   $250.80   $250.80  
  Purchase #6 $69.43   12.298%   $77.9685   $77.97   $77.95   $78.00  
  Purchase #7 $83.73   11.388%   $93.2652   $93.27   $93.25   $93.30  
  7 purchase totals = $1,123.32       $1,205.0405   $1,205.06   $1,205.05   $1,205.00