Let's do some math ..  Rounding examples of 9 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $119.58   11.209%   $132.9837   $132.98   $133.00   $133.00  
  Purchase #2 $226.32   6.692%   $241.4653   $241.47   $241.45   $241.50  
  Purchase #3 $243.92   4.442%   $254.7549   $254.75   $254.75   $254.80  
  Purchase #4 $225.72   3.486%   $233.5886   $233.59   $233.60   $233.60  
  Purchase #5 $118.62   13.436%   $134.5578   $134.56   $134.55   $134.60  
  Purchase #6 $156.67   3.535%   $162.2083   $162.21   $162.20   $162.20  
  Purchase #7 $33.68   3.491%   $34.8558   $34.86   $34.85   $34.90  
  Purchase #8 $219.35   3.766%   $227.6107   $227.61   $227.60   $227.60  
  Purchase #9 $19.62   12.164%   $22.0066   $22.01   $22.00   $22.00  
  9 purchase totals = $1,363.48       $1,444.04   $1,444.00   $1,444.20  
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?