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 $25.59   3.552%   $26.499   $26.50   $26.50   $26.50  
  Purchase #2 $54.82   13.236%   $62.076   $62.08   $62.10   $62.10  
  Purchase #3 $151.62   4.247%   $158.0593   $158.06   $158.05   $158.10  
  Purchase #4 $92.79   11.435%   $103.4005   $103.40   $103.40   $103.40  
  Purchase #5 $68.80   12.352%   $77.2982   $77.30   $77.30   $77.30  
  Purchase #6 $229.45   13.490%   $260.4028   $260.40   $260.40   $260.40  
  Purchase #7 $34.92   10.242%   $38.4965   $38.50   $38.50   $38.50  
  7 purchase totals = $657.99       $726.2323   $726.24   $726.25   $726.30