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 $191.45   8.564%   $207.8458   $207.85   $207.85   $207.80  
  Purchase #2 $58.86   5.838%   $62.2962   $62.30   $62.30   $62.30  
  Purchase #3 $56.71   6.749%   $60.5374   $60.54   $60.55   $60.50  
  Purchase #4 $134.42   8.657%   $146.0567   $146.06   $146.05   $146.10  
  Purchase #5 $150.53   7.613%   $161.9898   $161.99   $162.00   $162.00  
  Purchase #6 $32.67   7.666%   $35.1745   $35.17   $35.15   $35.20  
  Purchase #7 $242.99   10.703%   $268.9972   $269.00   $269.00   $269.00  
  7 purchase totals = $867.63       $942.8976   $942.91   $942.90   $942.90