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 $126.65   7.861%   $136.606   $136.61   $136.60   $136.60  
  Purchase #2 $105.63   7.225%   $113.2618   $113.26   $113.25   $113.30  
  Purchase #3 $81.60   6.138%   $86.6086   $86.61   $86.60   $86.60  
  Purchase #4 $101.81   3.819%   $105.6981   $105.70   $105.70   $105.70  
  Purchase #5 $214.95   5.152%   $226.0242   $226.02   $226.00   $226.00  
  Purchase #6 $80.27   8.625%   $87.1933   $87.19   $87.20   $87.20  
  Purchase #7 $184.67   7.525%   $198.5664   $198.57   $198.55   $198.60  
  7 purchase totals = $895.58       $953.9584   $953.96   $953.90   $954.00