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 $116.86   9.314%   $127.7443   $127.74   $127.75   $127.70  
  Purchase #2 $209.77   7.854%   $226.2453   $226.25   $226.25   $226.20  
  Purchase #3 $202.59   9.315%   $221.4613   $221.46   $221.45   $221.50  
  Purchase #4 $104.58   12.801%   $117.9673   $117.97   $117.95   $118.00  
  Purchase #5 $139.92   11.744%   $156.3522   $156.35   $156.35   $156.40  
  Purchase #6 $92.72   11.333%   $103.228   $103.23   $103.25   $103.20  
  Purchase #7 $157.97   3.348%   $163.2588   $163.26   $163.25   $163.30  
  7 purchase totals = $1,024.41       $1,116.2572   $1,116.26   $1,116.25   $1,116.30