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 $167.59   11.120%   $186.226   $186.23   $186.25   $186.20  
  Purchase #2 $235.56   4.495%   $246.1484   $246.15   $246.15   $246.10  
  Purchase #3 $221.78   8.665%   $240.9972   $241.00   $241.00   $241.00  
  Purchase #4 $55.25   3.219%   $57.0285   $57.03   $57.05   $57.00  
  Purchase #5 $249.62   8.808%   $271.6065   $271.61   $271.60   $271.60  
  Purchase #6 $184.34   5.848%   $195.1202   $195.12   $195.10   $195.10  
  Purchase #7 $36.72   8.822%   $39.9594   $39.96   $39.95   $40.00  
  7 purchase totals = $1,150.86       $1,237.0862   $1,237.10   $1,237.10   $1,237.00