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 $46.59   12.135%   $52.2437   $52.24   $52.25   $52.20  
  Purchase #2 $224.48   8.783%   $244.1961   $244.20   $244.20   $244.20  
  Purchase #3 $212.61   12.497%   $239.1799   $239.18   $239.20   $239.20  
  Purchase #4 $167.27   4.874%   $175.4227   $175.42   $175.40   $175.40  
  Purchase #5 $244.26   10.226%   $269.238   $269.24   $269.25   $269.20  
  Purchase #6 $46.38   12.265%   $52.0685   $52.07   $52.05   $52.10  
  Purchase #7 $153.29   6.516%   $163.2784   $163.28   $163.30   $163.30  
  7 purchase totals = $1,094.88       $1,195.6273   $1,195.63   $1,195.65   $1,195.60