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 $38.87   13.131%   $43.974   $43.97   $43.95   $44.00  
  Purchase #2 $216.31   6.318%   $229.9765   $229.98   $230.00   $230.00  
  Purchase #3 $25.41   4.668%   $26.5961   $26.60   $26.60   $26.60  
  Purchase #4 $55.79   5.199%   $58.6905   $58.69   $58.70   $58.70  
  Purchase #5 $214.56   9.384%   $234.6943   $234.69   $234.70   $234.70  
  Purchase #6 $203.72   4.610%   $213.1115   $213.11   $213.10   $213.10  
  Purchase #7 $249.96   4.552%   $261.3382   $261.34   $261.35   $261.30  
  7 purchase totals = $1,004.62       $1,068.3811   $1,068.38   $1,068.40   $1,068.40