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 $155.52   4.789%   $162.9679   $162.97   $162.95   $163.00  
  Purchase #2 $213.57   8.584%   $231.9028   $231.90   $231.90   $231.90  
  Purchase #3 $35.71   13.457%   $40.5155   $40.52   $40.50   $40.50  
  Purchase #4 $122.48   9.197%   $133.7445   $133.74   $133.75   $133.70  
  Purchase #5 $37.32   3.393%   $38.5863   $38.59   $38.60   $38.60  
  Purchase #6 $178.32   11.243%   $198.3685   $198.37   $198.35   $198.40  
  Purchase #7 $200.91   3.639%   $208.2211   $208.22   $208.20   $208.20  
  7 purchase totals = $943.83       $1,014.3066   $1,014.31   $1,014.25   $1,014.30