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 $62.98   6.359%   $66.9849   $66.98   $67.00   $67.00  
  Purchase #2 $229.28   13.404%   $260.0127   $260.01   $260.00   $260.00  
  Purchase #3 $72.69   6.401%   $77.3429   $77.34   $77.35   $77.30  
  Purchase #4 $90.79   3.172%   $93.6699   $93.67   $93.65   $93.70  
  Purchase #5 $231.61   13.316%   $262.4512   $262.45   $262.45   $262.50  
  Purchase #6 $228.85   11.406%   $254.9526   $254.95   $254.95   $255.00  
  Purchase #7 $21.87   12.181%   $24.534   $24.53   $24.55   $24.50  
  7 purchase totals = $938.07       $1,039.9482   $1,039.93   $1,039.95   $1,040.00