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 $193.71   10.479%   $214.0089   $214.01   $214.00   $214.00  
  Purchase #2 $63.42   5.116%   $66.6646   $66.66   $66.65   $66.70  
  Purchase #3 $44.34   4.199%   $46.2018   $46.20   $46.20   $46.20  
  Purchase #4 $237.99   10.131%   $262.1008   $262.10   $262.10   $262.10  
  Purchase #5 $162.66   10.342%   $179.4823   $179.48   $179.50   $179.50  
  Purchase #6 $60.49   3.457%   $62.5811   $62.58   $62.60   $62.60  
  Purchase #7 $115.65   10.493%   $127.7852   $127.79   $127.80   $127.80  
  7 purchase totals = $878.26       $958.8247   $958.82   $958.85   $958.90