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 $105.35   8.771%   $114.5902   $114.59   $114.60   $114.60  
  Purchase #2 $141.68   12.412%   $159.2653   $159.27   $159.25   $159.30  
  Purchase #3 $171.41   12.407%   $192.6768   $192.68   $192.70   $192.70  
  Purchase #4 $70.59   9.731%   $77.4591   $77.46   $77.45   $77.50  
  Purchase #5 $182.34   8.301%   $197.476   $197.48   $197.50   $197.50  
  Purchase #6 $199.26   4.232%   $207.6927   $207.69   $207.70   $207.70  
  Purchase #7 $17.55   7.703%   $18.9019   $18.90   $18.90   $18.90  
  7 purchase totals = $888.18       $968.0620   $968.07   $968.10   $968.20