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 $140.42   8.434%   $152.263   $152.26   $152.25   $152.30  
  Purchase #2 $176.65   6.860%   $188.7682   $188.77   $188.75   $188.80  
  Purchase #3 $237.46   13.351%   $269.1633   $269.16   $269.15   $269.20  
  Purchase #4 $95.59   8.212%   $103.4399   $103.44   $103.45   $103.40  
  Purchase #5 $164.40   11.862%   $183.9011   $183.90   $183.90   $183.90  
  Purchase #6 $99.33   3.254%   $102.5622   $102.56   $102.55   $102.60  
  Purchase #7 $141.44   10.640%   $156.4892   $156.49   $156.50   $156.50  
  7 purchase totals = $1,055.29       $1,156.5869   $1,156.58   $1,156.55   $1,156.70