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 $88.33   9.328%   $96.5694   $96.57   $96.55   $96.60  
  Purchase #2 $163.67   13.645%   $186.0028   $186.00   $186.00   $186.00  
  Purchase #3 $34.63   8.555%   $37.5926   $37.59   $37.60   $37.60  
  Purchase #4 $208.38   13.705%   $236.9385   $236.94   $236.95   $236.90  
  Purchase #5 $162.77   4.683%   $170.3925   $170.39   $170.40   $170.40  
  Purchase #6 $96.48   4.674%   $100.9895   $100.99   $101.00   $101.00  
  Purchase #7 $111.81   4.766%   $117.1389   $117.14   $117.15   $117.10  
  7 purchase totals = $866.07       $945.6242   $945.62   $945.65   $945.60