Let's do some math ..  Rounding examples of 10 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $209.51   6.366%   $222.8474   $222.85   $222.85   $222.80  
  Purchase #2 $88.41   5.425%   $93.2062   $93.21   $93.20   $93.20  
  Purchase #3 $117.95   8.631%   $128.1303   $128.13   $128.15   $128.10  
  Purchase #4 $110.80   4.341%   $115.6098   $115.61   $115.60   $115.60  
  Purchase #5 $180.92   4.388%   $188.8588   $188.86   $188.85   $188.90  
  Purchase #6 $107.90   4.607%   $112.871   $112.87   $112.85   $112.90  
  Purchase #7 $219.89   3.734%   $228.1007   $228.10   $228.10   $228.10  
  Purchase #8 $120.32   6.723%   $128.4091   $128.41   $128.40   $128.40  
  Purchase #9 $29.85   3.321%   $30.8413   $30.84   $30.85   $30.80  
  Purchase #10 $210.27   6.486%   $223.9081   $223.91   $223.90   $223.90  
  10 purchase totals = $1,395.82       $1,472.7827   $1,472.79   $1,472.75   $1,472.70  
Come on folks.. this just does not make any cents. We got rid of the 1/2 cent back in 1857.. Getting rid of the 1 cent coin is way, WAY past due. The penny has become a social and cultural anachronism. If our friends in Canada, Australia and a dozen other countries can stop the use of their pennies, why can't we?