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 $92.95   4.358%   $97.0008   $97.00   $97.00   $97.00  
  Purchase #2 $169.43   13.808%   $192.8249   $192.82   $192.80   $192.80  
  Purchase #3 $230.30   7.702%   $248.0377   $248.04   $248.05   $248.00  
  Purchase #4 $26.53   6.393%   $28.2261   $28.23   $28.25   $28.20  
  Purchase #5 $175.69   5.739%   $185.7728   $185.77   $185.75   $185.80  
  Purchase #6 $199.49   8.322%   $216.0916   $216.09   $216.10   $216.10  
  Purchase #7 $145.78   8.443%   $158.0882   $158.09   $158.10   $158.10  
  7 purchase totals = $1,040.17       $1,126.0421   $1,126.04   $1,126.05   $1,126.00