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 $188.59   13.469%   $213.9912   $213.99   $214.00   $214.00  
  Purchase #2 $171.89   13.870%   $195.7311   $195.73   $195.75   $195.70  
  Purchase #3 $97.29   11.840%   $108.8091   $108.81   $108.80   $108.80  
  Purchase #4 $173.56   7.495%   $186.5683   $186.57   $186.55   $186.60  
  Purchase #5 $34.32   4.531%   $35.875   $35.88   $35.90   $35.90  
  Purchase #6 $195.39   13.632%   $222.0256   $222.03   $222.05   $222.00  
  Purchase #7 $219.99   8.353%   $238.3658   $238.37   $238.35   $238.40  
  7 purchase totals = $1,081.03       $1,201.3661   $1,201.38   $1,201.40   $1,201.40