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 $22.98   13.829%   $26.1579   $26.16   $26.15   $26.20  
  Purchase #2 $193.76   7.440%   $208.1757   $208.18   $208.20   $208.20  
  Purchase #3 $217.37   12.237%   $243.9696   $243.97   $243.95   $244.00  
  Purchase #4 $152.81   9.106%   $166.7249   $166.72   $166.70   $166.70  
  Purchase #5 $142.56   6.204%   $151.4044   $151.40   $151.40   $151.40  
  Purchase #6 $167.68   9.579%   $183.7421   $183.74   $183.75   $183.70  
  Purchase #7 $137.83   6.195%   $146.3686   $146.37   $146.35   $146.40  
  7 purchase totals = $1,034.99       $1,126.5432   $1,126.54   $1,126.50   $1,126.60