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 $68.96   4.361%   $71.9673   $71.97   $71.95   $72.00  
  Purchase #2 $207.94   4.612%   $217.5302   $217.53   $217.55   $217.50  
  Purchase #3 $140.40   3.792%   $145.724   $145.72   $145.70   $145.70  
  Purchase #4 $173.43   3.517%   $179.5295   $179.53   $179.55   $179.50  
  Purchase #5 $94.41   13.839%   $107.4754   $107.48   $107.50   $107.50  
  Purchase #6 $151.99   10.827%   $168.446   $168.45   $168.45   $168.40  
  Purchase #7 $148.83   11.696%   $166.2372   $166.24   $166.25   $166.20  
  7 purchase totals = $985.96       $1,056.9096   $1,056.92   $1,056.95   $1,056.80