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 $57.29   9.639%   $62.8122   $62.81   $62.80   $62.80  
  Purchase #2 $214.98   10.600%   $237.7679   $237.77   $237.75   $237.80  
  Purchase #3 $56.60   11.201%   $62.9398   $62.94   $62.95   $62.90  
  Purchase #4 $248.45   7.383%   $266.7931   $266.79   $266.80   $266.80  
  Purchase #5 $30.69   4.375%   $32.0327   $32.03   $32.05   $32.00  
  Purchase #6 $58.67   11.631%   $65.4939   $65.49   $65.50   $65.50  
  Purchase #7 $211.30   11.770%   $236.17   $236.17   $236.15   $236.20  
  7 purchase totals = $877.98       $964.0096   $964.00   $964.00   $964.00