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 $248.47   5.174%   $261.3258   $261.33   $261.35   $261.30  
  Purchase #2 $111.77   6.548%   $119.0887   $119.09   $119.10   $119.10  
  Purchase #3 $60.41   13.435%   $68.5261   $68.53   $68.55   $68.50  
  Purchase #4 $183.52   7.215%   $196.761   $196.76   $196.75   $196.80  
  Purchase #5 $40.85   13.159%   $46.2255   $46.23   $46.25   $46.20  
  Purchase #6 $118.79   6.635%   $126.6717   $126.67   $126.65   $126.70  
  Purchase #7 $209.33   7.528%   $225.0884   $225.09   $225.10   $225.10  
  7 purchase totals = $973.14       $1,043.6872   $1,043.70   $1,043.75   $1,043.70