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 $95.57   3.203%   $98.6311   $98.63   $98.65   $98.60  
  Purchase #2 $71.89   5.702%   $75.9892   $75.99   $76.00   $76.00  
  Purchase #3 $211.43   11.531%   $235.81   $235.81   $235.80   $235.80  
  Purchase #4 $199.40   3.231%   $205.8426   $205.84   $205.85   $205.80  
  Purchase #5 $68.97   7.869%   $74.3972   $74.40   $74.40   $74.40  
  Purchase #6 $176.76   7.827%   $190.595   $190.60   $190.60   $190.60  
  Purchase #7 $212.68   5.563%   $224.5114   $224.51   $224.50   $224.50  
  7 purchase totals = $1,036.70       $1,105.7765   $1,105.78   $1,105.80   $1,105.70