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 $53.49   11.383%   $59.5788   $59.58   $59.60   $59.60  
  Purchase #2 $209.54   5.872%   $221.8442   $221.84   $221.85   $221.80  
  Purchase #3 $77.27   13.292%   $87.5407   $87.54   $87.55   $87.50  
  Purchase #4 $18.88   11.174%   $20.9897   $20.99   $21.00   $21.00  
  Purchase #5 $77.77   13.849%   $88.5404   $88.54   $88.55   $88.50  
  Purchase #6 $179.43   5.336%   $189.0044   $189.00   $189.00   $189.00  
  Purchase #7 $197.40   7.753%   $212.7044   $212.70   $212.70   $212.70  
  Purchase #8 $242.41   6.280%   $257.6333   $257.63   $257.65   $257.60  
  Purchase #9 $122.31   7.440%   $131.4099   $131.41   $131.40   $131.40  
  Purchase #10 $25.85   12.505%   $29.0825   $29.08   $29.10   $29.10  
  10 purchase totals = $1,204.35       $1,298.3283   $1,298.31   $1,298.40   $1,298.20  
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?