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 $57.66   7.562%   $62.0202   $62.02   $62.00   $62.00  
  Purchase #2 $95.88   6.398%   $102.0144   $102.01   $102.00   $102.00  
  Purchase #3 $60.93   7.274%   $65.362   $65.36   $65.35   $65.40  
  Purchase #4 $221.47   12.507%   $249.1693   $249.17   $249.15   $249.20  
  Purchase #5 $30.25   12.689%   $34.0884   $34.09   $34.10   $34.10  
  Purchase #6 $248.82   7.276%   $266.9241   $266.92   $266.90   $266.90  
  Purchase #7 $67.53   3.401%   $69.8267   $69.83   $69.85   $69.80  
  7 purchase totals = $782.54       $849.4051   $849.40   $849.35   $849.40