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 $85.25   11.558%   $95.1032   $95.10   $95.10   $95.10  
  Purchase #2 $234.68   11.620%   $261.9498   $261.95   $261.95   $261.90  
  Purchase #3 $62.46   7.395%   $67.0789   $67.08   $67.10   $67.10  
  Purchase #4 $136.91   11.466%   $152.6081   $152.61   $152.60   $152.60  
  Purchase #5 $25.92   3.545%   $26.8389   $26.84   $26.85   $26.80  
  Purchase #6 $100.86   12.430%   $113.3969   $113.40   $113.40   $113.40  
  Purchase #7 $78.75   9.640%   $86.3415   $86.34   $86.35   $86.30  
  7 purchase totals = $724.83       $803.3173   $803.32   $803.35   $803.20