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 $13.54   4.866%   $14.1989   $14.20   $14.20   $14.20  
  Purchase #2 $231.38   13.309%   $262.1744   $262.17   $262.15   $262.20  
  Purchase #3 $77.50   13.842%   $88.2276   $88.23   $88.25   $88.20  
  Purchase #4 $201.28   3.633%   $208.5925   $208.59   $208.60   $208.60  
  Purchase #5 $61.26   12.632%   $68.9984   $69.00   $69.00   $69.00  
  Purchase #6 $181.50   6.437%   $193.1832   $193.18   $193.20   $193.20  
  Purchase #7 $193.99   12.566%   $218.3668   $218.37   $218.35   $218.40  
  7 purchase totals = $960.45       $1,053.7418   $1,053.74   $1,053.75   $1,053.80