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 $62.52   3.478%   $64.6944   $64.69   $64.70   $64.70  
  Purchase #2 $50.26   12.519%   $56.552   $56.55   $56.55   $56.60  
  Purchase #3 $142.61   6.765%   $152.2576   $152.26   $152.25   $152.30  
  Purchase #4 $227.29   3.871%   $236.0884   $236.09   $236.10   $236.10  
  Purchase #5 $210.94   3.550%   $218.4284   $218.43   $218.45   $218.40  
  Purchase #6 $72.45   5.265%   $76.2645   $76.26   $76.25   $76.30  
  Purchase #7 $57.32   13.386%   $64.9929   $64.99   $65.00   $65.00  
  7 purchase totals = $823.39       $869.2782   $869.27   $869.30   $869.40