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 $92.69   13.606%   $105.3014   $105.30   $105.30   $105.30  
  Purchase #2 $176.65   3.331%   $182.5342   $182.53   $182.55   $182.50  
  Purchase #3 $249.28   4.509%   $260.52   $260.52   $260.50   $260.50  
  Purchase #4 $163.93   6.143%   $174.0002   $174.00   $174.00   $174.00  
  Purchase #5 $8.80   5.517%   $9.2855   $9.29   $9.30   $9.30  
  Purchase #6 $231.66   13.197%   $262.2322   $262.23   $262.25   $262.20  
  Purchase #7 $184.69   5.347%   $194.5654   $194.57   $194.55   $194.60  
  7 purchase totals = $1,107.70       $1,188.4389   $1,188.44   $1,188.45   $1,188.40