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 $20.87   7.164%   $22.3651   $22.37   $22.35   $22.40  
  Purchase #2 $139.55   9.153%   $152.323   $152.32   $152.30   $152.30  
  Purchase #3 $56.91   8.806%   $61.9215   $61.92   $61.90   $61.90  
  Purchase #4 $136.68   10.435%   $150.9426   $150.94   $150.95   $150.90  
  Purchase #5 $10.60   13.789%   $12.0616   $12.06   $12.05   $12.10  
  Purchase #6 $140.44   11.844%   $157.0737   $157.07   $157.05   $157.10  
  Purchase #7 $234.69   6.320%   $249.5224   $249.52   $249.50   $249.50  
  Purchase #8 $14.58   4.653%   $15.2584   $15.26   $15.25   $15.30  
  Purchase #9 $28.56   12.140%   $32.0272   $32.03   $32.05   $32.00  
  Purchase #10 $17.90   10.539%   $19.7865   $19.79   $19.80   $19.80  
  10 purchase totals = $800.78       $873.28   $873.20   $873.30  
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?