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 $180.54   8.169%   $195.2883   $195.29   $195.30   $195.30  
  Purchase #2 $124.83   7.787%   $134.5505   $134.55   $134.55   $134.60  
  Purchase #3 $97.53   8.288%   $105.6133   $105.61   $105.60   $105.60  
  Purchase #4 $221.37   7.705%   $238.4266   $238.43   $238.45   $238.40  
  Purchase #5 $182.38   3.117%   $188.0648   $188.06   $188.05   $188.10  
  Purchase #6 $130.97   5.201%   $137.7817   $137.78   $137.80   $137.80  
  Purchase #7 $78.62   7.735%   $84.7013   $84.70   $84.70   $84.70  
  7 purchase totals = $1,016.24       $1,084.4265   $1,084.42   $1,084.45   $1,084.50