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 $24.93   4.467%   $26.0436   $26.04   $26.05   $26.00  
  Purchase #2 $186.62   6.596%   $198.9295   $198.93   $198.95   $198.90  
  Purchase #3 $171.48   3.737%   $177.8882   $177.89   $177.90   $177.90  
  Purchase #4 $174.88   5.126%   $183.8443   $183.84   $183.85   $183.80  
  Purchase #5 $167.81   10.422%   $185.2992   $185.30   $185.30   $185.30  
  Purchase #6 $133.57   12.695%   $150.5267   $150.53   $150.55   $150.50  
  Purchase #7 $178.58   4.116%   $185.9304   $185.93   $185.95   $185.90  
  7 purchase totals = $1,037.87       $1,108.4619   $1,108.46   $1,108.55   $1,108.30