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 $181.58   13.276%   $205.6866   $205.69   $205.70   $205.70  
  Purchase #2 $71.26   3.688%   $73.8881   $73.89   $73.90   $73.90  
  Purchase #3 $248.36   7.131%   $266.0706   $266.07   $266.05   $266.10  
  Purchase #4 $47.51   10.186%   $52.3494   $52.35   $52.35   $52.30  
  Purchase #5 $183.62   6.197%   $194.9989   $195.00   $195.00   $195.00  
  Purchase #6 $50.94   8.444%   $55.2414   $55.24   $55.25   $55.20  
  Purchase #7 $247.32   4.525%   $258.5112   $258.51   $258.50   $258.50  
  7 purchase totals = $1,030.59       $1,106.7462   $1,106.75   $1,106.75   $1,106.70