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 $208.86   9.511%   $228.7247   $228.72   $228.70   $228.70  
  Purchase #2 $238.83   12.233%   $268.0461   $268.05   $268.05   $268.00  
  Purchase #3 $158.94   8.272%   $172.0875   $172.09   $172.10   $172.10  
  Purchase #4 $112.67   9.221%   $123.0593   $123.06   $123.05   $123.10  
  Purchase #5 $46.82   9.291%   $51.17   $51.17   $51.15   $51.20  
  Purchase #6 $68.25   11.363%   $76.0052   $76.01   $76.00   $76.00  
  Purchase #7 $42.83   5.766%   $45.2996   $45.30   $45.30   $45.30  
  7 purchase totals = $877.20       $964.3924   $964.40   $964.35   $964.40