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 $87.89   7.179%   $94.1996   $94.20   $94.20   $94.20  
  Purchase #2 $23.26   13.402%   $26.3773   $26.38   $26.40   $26.40  
  Purchase #3 $213.65   3.849%   $221.8734   $221.87   $221.85   $221.90  
  Purchase #4 $69.75   13.701%   $79.3064   $79.31   $79.30   $79.30  
  Purchase #5 $42.72   12.264%   $47.9592   $47.96   $47.95   $48.00  
  Purchase #6 $203.41   11.595%   $226.9954   $227.00   $227.00   $227.00  
  Purchase #7 $171.71   11.311%   $191.1321   $191.13   $191.15   $191.10  
  7 purchase totals = $812.39       $887.8434   $887.85   $887.85   $887.90