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 $187.95   3.742%   $194.9831   $194.98   $195.00   $195.00  
  Purchase #2 $49.27   3.424%   $50.957   $50.96   $50.95   $51.00  
  Purchase #3 $99.71   5.531%   $105.225   $105.23   $105.25   $105.20  
  Purchase #4 $208.95   9.831%   $229.4919   $229.49   $229.50   $229.50  
  Purchase #5 $59.83   7.704%   $64.4393   $64.44   $64.45   $64.40  
  Purchase #6 $33.49   4.516%   $35.0024   $35.00   $35.00   $35.00  
  Purchase #7 $89.63   10.346%   $98.9031   $98.90   $98.90   $98.90  
  7 purchase totals = $728.83       $779.0018   $779.00   $779.05   $779.00