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 $146.70   10.228%   $161.7045   $161.70   $161.70   $161.70  
  Purchase #2 $175.38   5.257%   $184.5997   $184.60   $184.60   $184.60  
  Purchase #3 $110.75   3.742%   $114.8943   $114.89   $114.90   $114.90  
  Purchase #4 $54.71   5.852%   $57.9116   $57.91   $57.90   $57.90  
  Purchase #5 $226.69   7.349%   $243.3494   $243.35   $243.35   $243.30  
  Purchase #6 $112.25   4.631%   $117.4483   $117.45   $117.45   $117.40  
  Purchase #7 $167.49   4.371%   $174.811   $174.81   $174.80   $174.80  
  7 purchase totals = $993.97       $1,054.7188   $1,054.71   $1,054.70   $1,054.60