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 $232.44   9.506%   $254.5357   $254.54   $254.55   $254.50  
  Purchase #2 $232.38   4.498%   $242.8325   $242.83   $242.85   $242.80  
  Purchase #3 $33.39   8.366%   $36.1834   $36.18   $36.20   $36.20  
  Purchase #4 $119.97   12.422%   $134.8727   $134.87   $134.85   $134.90  
  Purchase #5 $76.90   13.851%   $87.5514   $87.55   $87.55   $87.60  
  Purchase #6 $129.67   8.374%   $140.5286   $140.53   $140.55   $140.50  
  Purchase #7 $182.42   8.683%   $198.2595   $198.26   $198.25   $198.30  
  7 purchase totals = $1,007.17       $1,094.7638   $1,094.76   $1,094.80   $1,094.80