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 $246.65   6.221%   $261.9941   $261.99   $262.00   $262.00  
  Purchase #2 $223.38   5.258%   $235.1253   $235.13   $235.15   $235.10  
  Purchase #3 $66.72   5.285%   $70.2462   $70.25   $70.25   $70.20  
  Purchase #4 $111.31   7.734%   $119.9187   $119.92   $119.90   $119.90  
  Purchase #5 $62.31   4.529%   $65.132   $65.13   $65.15   $65.10  
  Purchase #6 $100.81   12.774%   $113.6875   $113.69   $113.70   $113.70  
  Purchase #7 $129.44   11.863%   $144.7955   $144.80   $144.80   $144.80  
  7 purchase totals = $940.62       $1,010.8993   $1,010.91   $1,010.95   $1,010.80