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 $219.44   11.241%   $244.1073   $244.11   $244.10   $244.10  
  Purchase #2 $10.38   10.681%   $11.4887   $11.49   $11.50   $11.50  
  Purchase #3 $77.65   7.548%   $83.511   $83.51   $83.50   $83.50  
  Purchase #4 $167.90   3.320%   $173.4743   $173.47   $173.45   $173.50  
  Purchase #5 $191.53   7.394%   $205.6917   $205.69   $205.70   $205.70  
  Purchase #6 $183.63   8.146%   $198.5885   $198.59   $198.60   $198.60  
  Purchase #7 $27.93   9.666%   $30.6297   $30.63   $30.65   $30.60  
  7 purchase totals = $878.46       $947.4912   $947.49   $947.50   $947.50