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 $43.97   13.591%   $49.946   $49.95   $49.95   $49.90  
  Purchase #2 $183.92   7.734%   $198.1444   $198.14   $198.15   $198.10  
  Purchase #3 $185.65   8.687%   $201.7774   $201.78   $201.80   $201.80  
  Purchase #4 $174.44   7.850%   $188.1335   $188.13   $188.15   $188.10  
  Purchase #5 $87.86   6.822%   $93.8538   $93.85   $93.85   $93.90  
  Purchase #6 $156.69   4.739%   $164.1155   $164.12   $164.10   $164.10  
  Purchase #7 $31.97   6.557%   $34.0663   $34.07   $34.05   $34.10  
  Purchase #8 $148.34   9.519%   $162.4605   $162.46   $162.45   $162.50  
  Purchase #9 $96.47   3.640%   $99.9815   $99.98   $100.00   $100.00  
  Purchase #10 $119.95   5.696%   $126.7824   $126.78   $126.80   $126.80  
  10 purchase totals = $1,229.26       $1,319.2613   $1,319.26   $1,319.30   $1,319.30  
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?