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 $205.46   5.861%   $217.502   $217.50   $217.50   $217.50  
  Purchase #2 $173.50   7.337%   $186.2297   $186.23   $186.25   $186.20  
  Purchase #3 $119.78   3.780%   $124.3077   $124.31   $124.30   $124.30  
  Purchase #4 $243.54   3.320%   $251.6255   $251.63   $251.65   $251.60  
  Purchase #5 $127.89   4.740%   $133.952   $133.95   $133.95   $134.00  
  Purchase #6 $107.64   5.826%   $113.9111   $113.91   $113.90   $113.90  
  Purchase #7 $18.72   11.381%   $20.8505   $20.85   $20.85   $20.90  
  7 purchase totals = $996.53       $1,048.3785   $1,048.38   $1,048.40   $1,048.40