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 $84.48   13.431%   $95.8265   $95.83   $95.85   $95.80  
  Purchase #2 $134.69   3.609%   $139.551   $139.55   $139.55   $139.60  
  Purchase #3 $62.45   9.475%   $68.3671   $68.37   $68.35   $68.40  
  Purchase #4 $79.68   7.797%   $85.8926   $85.89   $85.90   $85.90  
  Purchase #5 $171.97   3.714%   $178.357   $178.36   $178.35   $178.40  
  Purchase #6 $212.47   4.839%   $222.7514   $222.75   $222.75   $222.80  
  Purchase #7 $97.99   8.459%   $106.279   $106.28   $106.30   $106.30  
  7 purchase totals = $843.73       $897.0246   $897.03   $897.05   $897.20