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 $58.54   5.188%   $61.5771   $61.58   $61.60   $61.60  
  Purchase #2 $79.62   13.627%   $90.4698   $90.47   $90.45   $90.50  
  Purchase #3 $193.46   6.177%   $205.41   $205.41   $205.40   $205.40  
  Purchase #4 $91.82   3.175%   $94.7353   $94.74   $94.75   $94.70  
  Purchase #5 $220.72   9.555%   $241.8098   $241.81   $241.80   $241.80  
  Purchase #6 $241.69   13.422%   $274.1296   $274.13   $274.15   $274.10  
  Purchase #7 $211.33   7.490%   $227.1586   $227.16   $227.15   $227.20  
  7 purchase totals = $1,097.18       $1,195.2902   $1,195.30   $1,195.30   $1,195.30