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 $114.60   9.741%   $125.7632   $125.76   $125.75   $125.80  
  Purchase #2 $117.32   9.486%   $128.449   $128.45   $128.45   $128.40  
  Purchase #3 $176.37   7.108%   $188.9064   $188.91   $188.90   $188.90  
  Purchase #4 $98.54   6.831%   $105.2713   $105.27   $105.25   $105.30  
  Purchase #5 $162.63   8.539%   $176.517   $176.52   $176.50   $176.50  
  Purchase #6 $185.54   7.526%   $199.5037   $199.50   $199.50   $199.50  
  Purchase #7 $21.52   11.781%   $24.0553   $24.06   $24.05   $24.10  
  7 purchase totals = $876.52       $948.4659   $948.47   $948.40   $948.50