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 $86.49   9.433%   $94.6486   $94.65   $94.65   $94.60  
  Purchase #2 $55.61   3.544%   $57.5808   $57.58   $57.60   $57.60  
  Purchase #3 $119.38   4.255%   $124.4596   $124.46   $124.45   $124.50  
  Purchase #4 $52.89   10.571%   $58.481   $58.48   $58.50   $58.50  
  Purchase #5 $197.51   3.145%   $203.7217   $203.72   $203.70   $203.70  
  Purchase #6 $210.52   6.612%   $224.4396   $224.44   $224.45   $224.40  
  Purchase #7 $143.53   6.372%   $152.6757   $152.68   $152.70   $152.70  
  7 purchase totals = $865.93       $916.0070   $916.01   $916.05   $916.00