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 $208.82   13.794%   $237.6246   $237.62   $237.60   $237.60  
  Purchase #2 $142.71   8.447%   $154.7647   $154.76   $154.75   $154.80  
  Purchase #3 $11.58   7.278%   $12.4228   $12.42   $12.40   $12.40  
  Purchase #4 $18.34   4.705%   $19.2029   $19.20   $19.20   $19.20  
  Purchase #5 $234.58   13.836%   $267.0365   $267.04   $267.05   $267.00  
  Purchase #6 $217.27   9.166%   $237.185   $237.19   $237.20   $237.20  
  Purchase #7 $187.90   9.868%   $206.442   $206.44   $206.45   $206.40  
  7 purchase totals = $1,021.20       $1,134.6785   $1,134.67   $1,134.65   $1,134.60