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 $67.28   13.504%   $76.3655   $76.37   $76.35   $76.40  
  Purchase #2 $162.30   10.856%   $179.9193   $179.92   $179.90   $179.90  
  Purchase #3 $187.53   5.493%   $197.831   $197.83   $197.85   $197.80  
  Purchase #4 $62.31   12.523%   $70.1131   $70.11   $70.10   $70.10  
  Purchase #5 $179.74   9.517%   $196.8459   $196.85   $196.85   $196.80  
  Purchase #6 $157.95   10.307%   $174.2299   $174.23   $174.25   $174.20  
  Purchase #7 $33.46   10.458%   $36.9592   $36.96   $36.95   $37.00  
  7 purchase totals = $850.57       $932.2639   $932.27   $932.25   $932.20