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 $151.27   3.479%   $156.5327   $156.53   $156.55   $156.50  
  Purchase #2 $55.77   11.491%   $62.1785   $62.18   $62.20   $62.20  
  Purchase #3 $223.38   5.157%   $234.8997   $234.90   $234.90   $234.90  
  Purchase #4 $114.57   10.427%   $126.5162   $126.52   $126.50   $126.50  
  Purchase #5 $250.36   7.368%   $268.8065   $268.81   $268.80   $268.80  
  Purchase #6 $26.42   4.646%   $27.6475   $27.65   $27.65   $27.60  
  Purchase #7 $175.28   10.155%   $193.0797   $193.08   $193.10   $193.10  
  7 purchase totals = $997.05       $1,069.6608   $1,069.67   $1,069.70   $1,069.60