Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $62.86   13.450%   $71.3147   $71.31   $71.30   $71.30  
  Purchase #2 $147.53   6.213%   $156.696   $156.70   $156.70   $156.70  
  Purchase #3 $117.46   4.621%   $122.8878   $122.89   $122.90   $122.90  
  Purchase #4 $11.88   13.506%   $13.4845   $13.48   $13.50   $13.50  
  Purchase #5 $56.99   9.245%   $62.2587   $62.26   $62.25   $62.30  
  Purchase #6 $178.64   13.472%   $202.7064   $202.71   $202.70   $202.70  
  Purchase #7 $187.84   10.605%   $207.7604   $207.76   $207.75   $207.80  
  7 purchase totals = $763.20       $837.1085   $837.11   $837.10   $837.20