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 $223.38   9.503%   $244.6078   $244.61   $244.60   $244.60  
  Purchase #2 $98.89   10.436%   $109.2102   $109.21   $109.20   $109.20  
  Purchase #3 $217.31   12.616%   $244.7258   $244.73   $244.75   $244.70  
  Purchase #4 $109.91   8.798%   $119.5799   $119.58   $119.60   $119.60  
  Purchase #5 $235.90   7.173%   $252.8211   $252.82   $252.80   $252.80  
  Purchase #6 $58.72   8.730%   $63.8463   $63.85   $63.85   $63.80  
  Purchase #7 $203.56   11.138%   $226.2325   $226.23   $226.25   $226.20  
  7 purchase totals = $1,147.67       $1,261.0236   $1,261.03   $1,261.05   $1,260.90