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 $54.64   13.866%   $62.2164   $62.22   $62.20   $62.20  
  Purchase #2 $241.83   7.245%   $259.3506   $259.35   $259.35   $259.40  
  Purchase #3 $104.43   4.548%   $109.1795   $109.18   $109.20   $109.20  
  Purchase #4 $17.48   10.166%   $19.257   $19.26   $19.25   $19.30  
  Purchase #5 $54.94   11.331%   $61.1653   $61.17   $61.15   $61.20  
  Purchase #6 $184.44   4.797%   $193.2876   $193.29   $193.30   $193.30  
  Purchase #7 $17.76   11.170%   $19.7438   $19.74   $19.75   $19.70  
  7 purchase totals = $675.52       $724.2002   $724.21   $724.20   $724.30