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 $23.81   3.136%   $24.5567   $24.56   $24.55   $24.60  
  Purchase #2 $175.72   11.609%   $196.1193   $196.12   $196.10   $196.10  
  Purchase #3 $52.59   11.171%   $58.4648   $58.46   $58.45   $58.50  
  Purchase #4 $92.58   5.486%   $97.6589   $97.66   $97.65   $97.70  
  Purchase #5 $101.62   12.113%   $113.9292   $113.93   $113.95   $113.90  
  Purchase #6 $200.95   7.472%   $215.965   $215.97   $215.95   $216.00  
  Purchase #7 $195.54   3.750%   $202.8728   $202.87   $202.85   $202.90  
  7 purchase totals = $842.81       $909.5667   $909.57   $909.50   $909.70