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 $92.40   4.624%   $96.6726   $96.67   $96.65   $96.70  
  Purchase #2 $152.34   3.108%   $157.0747   $157.07   $157.05   $157.10  
  Purchase #3 $102.38   11.372%   $114.0227   $114.02   $114.00   $114.00  
  Purchase #4 $206.71   3.381%   $213.6989   $213.70   $213.70   $213.70  
  Purchase #5 $11.68   10.534%   $12.9104   $12.91   $12.90   $12.90  
  Purchase #6 $97.88   4.145%   $101.9371   $101.94   $101.95   $101.90  
  Purchase #7 $167.70   4.579%   $175.379   $175.38   $175.40   $175.40  
  7 purchase totals = $831.09       $871.6954   $871.69   $871.65   $871.70