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 $59.56   10.269%   $65.6762   $65.68   $65.70   $65.70  
  Purchase #2 $217.45   4.536%   $227.3135   $227.31   $227.30   $227.30  
  Purchase #3 $39.96   3.273%   $41.2679   $41.27   $41.25   $41.30  
  Purchase #4 $195.70   5.354%   $206.1778   $206.18   $206.20   $206.20  
  Purchase #5 $21.74   10.469%   $24.016   $24.02   $24.00   $24.00  
  Purchase #6 $247.35   5.728%   $261.5182   $261.52   $261.50   $261.50  
  Purchase #7 $241.96   8.114%   $261.5926   $261.59   $261.60   $261.60  
  7 purchase totals = $1,023.72       $1,087.5622   $1,087.57   $1,087.55   $1,087.60