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 $201.36   6.522%   $214.4927   $214.49   $214.50   $214.50  
  Purchase #2 $65.42   6.508%   $69.6775   $69.68   $69.70   $69.70  
  Purchase #3 $87.63   7.349%   $94.0699   $94.07   $94.05   $94.10  
  Purchase #4 $200.82   3.776%   $208.403   $208.40   $208.40   $208.40  
  Purchase #5 $26.52   10.807%   $29.386   $29.39   $29.40   $29.40  
  Purchase #6 $186.76   4.483%   $195.1325   $195.13   $195.15   $195.10  
  Purchase #7 $47.46   8.434%   $51.4628   $51.46   $51.45   $51.50  
  7 purchase totals = $815.97       $862.6244   $862.62   $862.65   $862.70