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 $191.88   11.521%   $213.9865   $213.99   $214.00   $214.00  
  Purchase #2 $45.50   13.466%   $51.627   $51.63   $51.65   $51.60  
  Purchase #3 $52.27   3.379%   $54.0362   $54.04   $54.05   $54.00  
  Purchase #4 $230.79   13.219%   $261.2981   $261.30   $261.30   $261.30  
  Purchase #5 $169.63   9.423%   $185.6142   $185.61   $185.60   $185.60  
  Purchase #6 $209.30   5.163%   $220.1062   $220.11   $220.10   $220.10  
  Purchase #7 $55.57   12.367%   $62.4423   $62.44   $62.45   $62.40  
  7 purchase totals = $954.94       $1,049.1105   $1,049.12   $1,049.15   $1,049.00