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 $203.89   4.395%   $212.851   $212.85   $212.85   $212.90  
  Purchase #2 $188.80   4.750%   $197.768   $197.77   $197.75   $197.80  
  Purchase #3 $98.93   5.779%   $104.6472   $104.65   $104.65   $104.60  
  Purchase #4 $69.66   7.512%   $74.8929   $74.89   $74.90   $74.90  
  Purchase #5 $77.49   13.551%   $87.9907   $87.99   $88.00   $88.00  
  Purchase #6 $233.98   12.662%   $263.6065   $263.61   $263.60   $263.60  
  Purchase #7 $24.80   5.102%   $26.0653   $26.07   $26.05   $26.10  
  7 purchase totals = $897.55       $967.8216   $967.83   $967.80   $967.90