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 $54.98   11.204%   $61.14   $61.14   $61.15   $61.10  
  Purchase #2 $200.41   8.394%   $217.2324   $217.23   $217.25   $217.20  
  Purchase #3 $169.56   9.493%   $185.6563   $185.66   $185.65   $185.70  
  Purchase #4 $94.91   7.292%   $101.8308   $101.83   $101.85   $101.80  
  Purchase #5 $97.45   5.181%   $102.4989   $102.50   $102.50   $102.50  
  Purchase #6 $29.38   11.291%   $32.6973   $32.70   $32.70   $32.70  
  Purchase #7 $230.93   13.137%   $261.2673   $261.27   $261.25   $261.30  
  7 purchase totals = $877.62       $962.3230   $962.33   $962.35   $962.30