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 $214.66   9.543%   $235.145   $235.15   $235.15   $235.10  
  Purchase #2 $57.38   7.620%   $61.7524   $61.75   $61.75   $61.80  
  Purchase #3 $100.32   12.538%   $112.8981   $112.90   $112.90   $112.90  
  Purchase #4 $198.65   9.349%   $217.2218   $217.22   $217.20   $217.20  
  Purchase #5 $95.36   11.162%   $106.0041   $106.00   $106.00   $106.00  
  Purchase #6 $184.66   9.508%   $202.2175   $202.22   $202.20   $202.20  
  Purchase #7 $16.28   9.665%   $17.8535   $17.85   $17.85   $17.90  
  7 purchase totals = $867.31       $953.0924   $953.09   $953.05   $953.10