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 $61.85   11.735%   $69.1081   $69.11   $69.10   $69.10  
  Purchase #2 $223.91   6.126%   $237.6267   $237.63   $237.65   $237.60  
  Purchase #3 $162.31   9.301%   $177.4065   $177.41   $177.40   $177.40  
  Purchase #4 $31.98   7.725%   $34.4505   $34.45   $34.45   $34.50  
  Purchase #5 $241.99   13.263%   $274.0851   $274.09   $274.10   $274.10  
  Purchase #6 $165.94   13.844%   $188.9127   $188.91   $188.90   $188.90  
  Purchase #7 $52.44   4.251%   $54.6692   $54.67   $54.65   $54.70  
  7 purchase totals = $940.42       $1,036.2588   $1,036.27   $1,036.25   $1,036.30