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 $176.70   3.122%   $182.2166   $182.22   $182.20   $182.20  
  Purchase #2 $248.96   11.480%   $277.5406   $277.54   $277.55   $277.50  
  Purchase #3 $44.61   4.535%   $46.6331   $46.63   $46.65   $46.60  
  Purchase #4 $205.58   3.244%   $212.249   $212.25   $212.25   $212.20  
  Purchase #5 $81.48   9.748%   $89.4227   $89.42   $89.40   $89.40  
  Purchase #6 $150.39   9.195%   $164.2184   $164.22   $164.20   $164.20  
  Purchase #7 $135.41   3.574%   $140.2496   $140.25   $140.25   $140.20  
  7 purchase totals = $1,043.13       $1,112.5300   $1,112.53   $1,112.50   $1,112.30