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 $46.83   6.635%   $49.9372   $49.94   $49.95   $49.90  
  Purchase #2 $179.87   9.862%   $197.6088   $197.61   $197.60   $197.60  
  Purchase #3 $108.51   5.531%   $114.5117   $114.51   $114.50   $114.50  
  Purchase #4 $103.99   5.453%   $109.6606   $109.66   $109.65   $109.70  
  Purchase #5 $147.63   11.275%   $164.2753   $164.28   $164.30   $164.30  
  Purchase #6 $151.57   10.294%   $167.1726   $167.17   $167.15   $167.20  
  Purchase #7 $141.41   12.675%   $159.3337   $159.33   $159.35   $159.30  
  7 purchase totals = $879.81       $962.4999   $962.50   $962.50   $962.50