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 $95.26   10.448%   $105.2128   $105.21   $105.20   $105.20  
  Purchase #2 $70.42   8.495%   $76.4022   $76.40   $76.40   $76.40  
  Purchase #3 $237.26   8.359%   $257.0926   $257.09   $257.10   $257.10  
  Purchase #4 $75.46   11.259%   $83.956   $83.96   $83.95   $84.00  
  Purchase #5 $66.69   3.689%   $69.1502   $69.15   $69.15   $69.20  
  Purchase #6 $233.58   5.547%   $246.5367   $246.54   $246.55   $246.50  
  Purchase #7 $207.52   10.649%   $229.6188   $229.62   $229.60   $229.60  
  7 purchase totals = $986.19       $1,067.9693   $1,067.97   $1,067.95   $1,068.00