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 $67.37   13.445%   $76.4279   $76.43   $76.45   $76.40  
  Purchase #2 $147.38   5.851%   $156.0032   $156.00   $156.00   $156.00  
  Purchase #3 $73.73   4.322%   $76.9166   $76.92   $76.90   $76.90  
  Purchase #4 $41.69   12.424%   $46.8696   $46.87   $46.85   $46.90  
  Purchase #5 $97.34   6.738%   $103.8988   $103.90   $103.90   $103.90  
  Purchase #6 $97.61   4.327%   $101.8336   $101.83   $101.85   $101.80  
  Purchase #7 $208.95   10.631%   $231.1635   $231.16   $231.15   $231.20  
  7 purchase totals = $734.07       $793.1132   $793.11   $793.10   $793.10