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 $92.28   5.508%   $97.3628   $97.36   $97.35   $97.40  
  Purchase #2 $224.81   6.380%   $239.1529   $239.15   $239.15   $239.20  
  Purchase #3 $214.88   8.665%   $233.4994   $233.50   $233.50   $233.50  
  Purchase #4 $57.26   9.538%   $62.7215   $62.72   $62.70   $62.70  
  Purchase #5 $54.90   6.740%   $58.6003   $58.60   $58.60   $58.60  
  Purchase #6 $114.32   4.199%   $119.1203   $119.12   $119.10   $119.10  
  Purchase #7 $147.46   6.481%   $157.0169   $157.02   $157.00   $157.00  
  7 purchase totals = $905.91       $967.4741   $967.47   $967.40   $967.50