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 $86.81   8.697%   $94.3599   $94.36   $94.35   $94.40  
  Purchase #2 $24.59   10.631%   $27.2042   $27.20   $27.20   $27.20  
  Purchase #3 $118.62   5.177%   $124.761   $124.76   $124.75   $124.80  
  Purchase #4 $228.26   9.771%   $250.5633   $250.56   $250.55   $250.60  
  Purchase #5 $72.37   13.478%   $82.124   $82.12   $82.10   $82.10  
  Purchase #6 $219.38   11.815%   $245.2997   $245.30   $245.30   $245.30  
  Purchase #7 $71.77   7.749%   $77.3315   $77.33   $77.35   $77.30  
  7 purchase totals = $821.80       $901.6436   $901.63   $901.60   $901.70