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 $208.91   9.771%   $229.3226   $229.32   $229.30   $229.30  
  Purchase #2 $168.33   9.219%   $183.8483   $183.85   $183.85   $183.80  
  Purchase #3 $211.44   10.676%   $234.0133   $234.01   $234.00   $234.00  
  Purchase #4 $86.68   4.430%   $90.5199   $90.52   $90.50   $90.50  
  Purchase #5 $128.97   5.503%   $136.0672   $136.07   $136.05   $136.10  
  Purchase #6 $147.34   7.575%   $158.501   $158.50   $158.50   $158.50  
  Purchase #7 $185.47   5.138%   $194.9994   $195.00   $195.00   $195.00  
  7 purchase totals = $1,137.14       $1,227.2717   $1,227.27   $1,227.20   $1,227.20