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 $95.58   8.614%   $103.8133   $103.81   $103.80   $103.80  
  Purchase #2 $240.73   8.831%   $261.9889   $261.99   $262.00   $262.00  
  Purchase #3 $53.47   3.736%   $55.4676   $55.47   $55.45   $55.50  
  Purchase #4 $175.82   5.156%   $184.8853   $184.89   $184.90   $184.90  
  Purchase #5 $182.87   10.651%   $202.3475   $202.35   $202.35   $202.30  
  Purchase #6 $55.89   3.386%   $57.7824   $57.78   $57.80   $57.80  
  Purchase #7 $244.53   9.169%   $266.951   $266.95   $266.95   $267.00  
  7 purchase totals = $1,048.89       $1,133.2360   $1,133.24   $1,133.25   $1,133.30