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 $208.29   5.703%   $220.1688   $220.17   $220.15   $220.20  
  Purchase #2 $167.47   11.416%   $186.5884   $186.59   $186.60   $186.60  
  Purchase #3 $157.90   10.358%   $174.2553   $174.26   $174.25   $174.30  
  Purchase #4 $34.88   6.454%   $37.1312   $37.13   $37.15   $37.10  
  Purchase #5 $130.26   3.439%   $134.7396   $134.74   $134.75   $134.70  
  Purchase #6 $111.54   13.853%   $126.9916   $126.99   $127.00   $127.00  
  Purchase #7 $229.49   7.262%   $246.1556   $246.16   $246.15   $246.20  
  7 purchase totals = $1,039.83       $1,126.0305   $1,126.04   $1,126.05   $1,126.10