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 $92.89   3.584%   $96.2192   $96.22   $96.20   $96.20  
  Purchase #2 $176.37   11.397%   $196.4709   $196.47   $196.45   $196.50  
  Purchase #3 $89.65   3.705%   $92.9715   $92.97   $92.95   $93.00  
  Purchase #4 $159.63   13.402%   $181.0236   $181.02   $181.00   $181.00  
  Purchase #5 $104.25   4.702%   $109.1518   $109.15   $109.15   $109.20  
  Purchase #6 $24.48   9.673%   $26.848   $26.85   $26.85   $26.80  
  Purchase #7 $173.69   11.537%   $193.7286   $193.73   $193.75   $193.70  
  7 purchase totals = $820.96       $896.4136   $896.41   $896.35   $896.40