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 $196.45   10.441%   $216.9613   $216.96   $216.95   $217.00  
  Purchase #2 $229.93   7.572%   $247.3403   $247.34   $247.35   $247.30  
  Purchase #3 $175.36   4.572%   $183.3775   $183.38   $183.40   $183.40  
  Purchase #4 $220.34   11.234%   $245.093   $245.09   $245.10   $245.10  
  Purchase #5 $124.81   4.508%   $130.4364   $130.44   $130.45   $130.40  
  Purchase #6 $82.96   4.382%   $86.5953   $86.60   $86.60   $86.60  
  Purchase #7 $52.82   6.476%   $56.2406   $56.24   $56.25   $56.20  
  7 purchase totals = $1,082.67       $1,166.0444   $1,166.05   $1,166.10   $1,166.00