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 $47.57   3.726%   $49.3425   $49.34   $49.35   $49.30  
  Purchase #2 $232.48   12.408%   $261.3261   $261.33   $261.35   $261.30  
  Purchase #3 $237.71   11.867%   $265.919   $265.92   $265.90   $265.90  
  Purchase #4 $119.41   6.581%   $127.2684   $127.27   $127.25   $127.30  
  Purchase #5 $150.88   9.471%   $165.1698   $165.17   $165.15   $165.20  
  Purchase #6 $47.82   7.153%   $51.2406   $51.24   $51.25   $51.20  
  Purchase #7 $177.35   9.381%   $193.9872   $193.99   $194.00   $194.00  
  7 purchase totals = $1,013.22       $1,114.2536   $1,114.26   $1,114.25   $1,114.20