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 $48.64   6.103%   $51.6085   $51.61   $51.60   $51.60  
  Purchase #2 $175.28   10.113%   $193.0061   $193.01   $193.00   $193.00  
  Purchase #3 $178.95   10.421%   $197.5984   $197.60   $197.60   $197.60  
  Purchase #4 $42.78   7.191%   $45.8563   $45.86   $45.85   $45.90  
  Purchase #5 $141.57   7.299%   $151.9032   $151.90   $151.90   $151.90  
  Purchase #6 $239.52   3.593%   $248.126   $248.13   $248.15   $248.10  
  Purchase #7 $6.30   13.546%   $7.1534   $7.15   $7.15   $7.20  
  7 purchase totals = $833.04       $895.2519   $895.26   $895.25   $895.30