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 $15.30   9.805%   $16.8002   $16.80   $16.80   $16.80  
  Purchase #2 $9.81   12.544%   $11.0406   $11.04   $11.05   $11.00  
  Purchase #3 $173.43   4.533%   $181.2916   $181.29   $181.30   $181.30  
  Purchase #4 $71.63   4.231%   $74.6607   $74.66   $74.65   $74.70  
  Purchase #5 $59.67   10.385%   $65.8667   $65.87   $65.85   $65.90  
  Purchase #6 $210.33   4.370%   $219.5214   $219.52   $219.50   $219.50  
  Purchase #7 $117.57   6.666%   $125.4072   $125.41   $125.40   $125.40  
  Purchase #8 $145.75   4.345%   $152.0828   $152.08   $152.10   $152.10  
  Purchase #9 $145.53   3.328%   $150.3732   $150.37   $150.35   $150.40  
  Purchase #10 $86.92   12.413%   $97.7094   $97.71   $97.70   $97.70  
  10 purchase totals = $1,035.94       $1,094.7538   $1,094.75   $1,094.70   $1,094.80  
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?