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 $22.64   10.710%   $25.0647   $25.06   $25.05   $25.10  
  Purchase #2 $242.76   7.667%   $261.3724   $261.37   $261.35   $261.40  
  Purchase #3 $94.30   11.429%   $105.0775   $105.08   $105.10   $105.10  
  Purchase #4 $167.37   4.801%   $175.4054   $175.41   $175.40   $175.40  
  Purchase #5 $198.56   9.731%   $217.8819   $217.88   $217.90   $217.90  
  Purchase #6 $159.49   12.537%   $179.4853   $179.49   $179.50   $179.50  
  Purchase #7 $75.25   5.489%   $79.3805   $79.38   $79.40   $79.40  
  7 purchase totals = $960.37       $1,043.6677   $1,043.67   $1,043.70   $1,043.80