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 $125.88   12.762%   $141.9448   $141.94   $141.95   $141.90  
  Purchase #2 $88.95   4.211%   $92.6957   $92.70   $92.70   $92.70  
  Purchase #3 $12.56   11.455%   $13.9987   $14.00   $14.00   $14.00  
  Purchase #4 $114.82   12.105%   $128.719   $128.72   $128.70   $128.70  
  Purchase #5 $201.60   5.622%   $212.934   $212.93   $212.95   $212.90  
  Purchase #6 $101.87   5.313%   $107.2824   $107.28   $107.30   $107.30  
  Purchase #7 $34.78   11.543%   $38.7947   $38.79   $38.80   $38.80  
  7 purchase totals = $680.46       $736.3693   $736.36   $736.40   $736.30