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 $174.79   11.103%   $194.1969   $194.20   $194.20   $194.20  
  Purchase #2 $70.70   7.656%   $76.1128   $76.11   $76.10   $76.10  
  Purchase #3 $66.94   7.480%   $71.9471   $71.95   $71.95   $71.90  
  Purchase #4 $33.89   7.278%   $36.3565   $36.36   $36.35   $36.40  
  Purchase #5 $33.44   5.433%   $35.2568   $35.26   $35.25   $35.30  
  Purchase #6 $111.51   11.543%   $124.3816   $124.38   $124.40   $124.40  
  Purchase #7 $230.37   4.497%   $240.7297   $240.73   $240.75   $240.70  
  7 purchase totals = $721.64       $778.9814   $778.99   $779.00   $779.00