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 $207.75   13.242%   $235.2603   $235.26   $235.25   $235.30  
  Purchase #2 $209.97   9.492%   $229.9004   $229.90   $229.90   $229.90  
  Purchase #3 $163.38   6.180%   $173.4769   $173.48   $173.50   $173.50  
  Purchase #4 $110.28   3.834%   $114.5081   $114.51   $114.50   $114.50  
  Purchase #5 $36.56   12.666%   $41.1907   $41.19   $41.20   $41.20  
  Purchase #6 $7.49   7.227%   $8.0313   $8.03   $8.05   $8.00  
  Purchase #7 $230.67   9.245%   $251.9954   $252.00   $252.00   $252.00  
  7 purchase totals = $966.10       $1,054.3631   $1,054.37   $1,054.40   $1,054.40