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 $219.74   7.277%   $235.7305   $235.73   $235.75   $235.70  
  Purchase #2 $220.41   13.473%   $250.1058   $250.11   $250.10   $250.10  
  Purchase #3 $222.54   9.754%   $244.2466   $244.25   $244.25   $244.20  
  Purchase #4 $26.73   12.527%   $30.0785   $30.08   $30.10   $30.10  
  Purchase #5 $141.82   6.654%   $151.2567   $151.26   $151.25   $151.30  
  Purchase #6 $94.29   11.832%   $105.4464   $105.45   $105.45   $105.40  
  Purchase #7 $133.63   13.863%   $152.1551   $152.16   $152.15   $152.20  
  7 purchase totals = $1,059.16       $1,169.0196   $1,169.04   $1,169.05   $1,169.00