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 $62.34   5.461%   $65.7444   $65.74   $65.75   $65.70  
  Purchase #2 $123.52   5.449%   $130.2506   $130.25   $130.25   $130.30  
  Purchase #3 $218.48   4.682%   $228.7092   $228.71   $228.70   $228.70  
  Purchase #4 $228.98   8.249%   $247.8686   $247.87   $247.85   $247.90  
  Purchase #5 $163.66   8.857%   $178.1554   $178.16   $178.15   $178.20  
  Purchase #6 $40.99   10.115%   $45.1361   $45.14   $45.15   $45.10  
  Purchase #7 $61.65   11.309%   $68.622   $68.62   $68.60   $68.60  
  7 purchase totals = $899.62       $964.4863   $964.49   $964.45   $964.50