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 $61.38   13.359%   $69.5798   $69.58   $69.60   $69.60  
  Purchase #2 $187.72   3.821%   $194.8928   $194.89   $194.90   $194.90  
  Purchase #3 $211.63   4.205%   $220.529   $220.53   $220.55   $220.50  
  Purchase #4 $41.33   12.458%   $46.4789   $46.48   $46.50   $46.50  
  Purchase #5 $230.45   8.754%   $250.6236   $250.62   $250.60   $250.60  
  Purchase #6 $95.71   5.729%   $101.1932   $101.19   $101.20   $101.20  
  Purchase #7 $221.44   7.382%   $237.7867   $237.79   $237.80   $237.80  
  7 purchase totals = $1,049.66       $1,121.0840   $1,121.08   $1,121.15   $1,121.10