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 $214.80   8.578%   $233.2255   $233.23   $233.25   $233.20  
  Purchase #2 $97.57   11.687%   $108.973   $108.97   $108.95   $109.00  
  Purchase #3 $215.28   4.248%   $224.4251   $224.43   $224.45   $224.40  
  Purchase #4 $146.71   3.241%   $151.4649   $151.46   $151.45   $151.50  
  Purchase #5 $119.29   9.449%   $130.5617   $130.56   $130.55   $130.60  
  Purchase #6 $248.44   7.524%   $267.1326   $267.13   $267.15   $267.10  
  Purchase #7 $217.53   10.286%   $239.9051   $239.91   $239.90   $239.90  
  7 purchase totals = $1,259.62       $1,355.6879   $1,355.69   $1,355.70   $1,355.70