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 $162.62   12.241%   $182.5263   $182.53   $182.55   $182.50  
  Purchase #2 $121.91   11.560%   $136.0028   $136.00   $136.00   $136.00  
  Purchase #3 $40.87   10.752%   $45.2643   $45.26   $45.25   $45.30  
  Purchase #4 $249.44   3.437%   $258.0133   $258.01   $258.00   $258.00  
  Purchase #5 $163.47   13.317%   $185.2393   $185.24   $185.25   $185.20  
  Purchase #6 $166.65   9.441%   $182.3834   $182.38   $182.40   $182.40  
  Purchase #7 $149.27   3.236%   $154.1004   $154.10   $154.10   $154.10  
  7 purchase totals = $1,054.23       $1,143.5298   $1,143.52   $1,143.55   $1,143.50