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 $92.68   3.151%   $95.6003   $95.60   $95.60   $95.60  
  Purchase #2 $171.28   9.676%   $187.8531   $187.85   $187.85   $187.90  
  Purchase #3 $36.71   9.712%   $40.2753   $40.28   $40.30   $40.30  
  Purchase #4 $95.61   10.336%   $105.4922   $105.49   $105.50   $105.50  
  Purchase #5 $169.83   11.352%   $189.1091   $189.11   $189.10   $189.10  
  Purchase #6 $124.68   9.353%   $136.3413   $136.34   $136.35   $136.30  
  Purchase #7 $177.58   11.262%   $197.5791   $197.58   $197.60   $197.60  
  7 purchase totals = $868.37       $952.2504   $952.25   $952.30   $952.30