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 $61.26   13.522%   $69.5436   $69.54   $69.55   $69.50  
  Purchase #2 $48.97   13.212%   $55.4399   $55.44   $55.45   $55.40  
  Purchase #3 $42.49   7.527%   $45.6882   $45.69   $45.70   $45.70  
  Purchase #4 $232.28   5.621%   $245.3365   $245.34   $245.35   $245.30  
  Purchase #5 $66.55   12.241%   $74.6964   $74.70   $74.70   $74.70  
  Purchase #6 $228.33   9.384%   $249.7565   $249.76   $249.75   $249.80  
  Purchase #7 $42.88   4.316%   $44.7307   $44.73   $44.75   $44.70  
  7 purchase totals = $722.76       $785.1918   $785.20   $785.25   $785.10