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 $119.25   5.335%   $125.612   $125.61   $125.60   $125.60  
  Purchase #2 $154.80   10.438%   $170.958   $170.96   $170.95   $171.00  
  Purchase #3 $114.82   13.771%   $130.6319   $130.63   $130.65   $130.60  
  Purchase #4 $153.27   5.110%   $161.1021   $161.10   $161.10   $161.10  
  Purchase #5 $82.85   6.296%   $88.0662   $88.07   $88.05   $88.10  
  Purchase #6 $134.28   8.452%   $145.6293   $145.63   $145.65   $145.60  
  Purchase #7 $194.31   6.511%   $206.9615   $206.96   $206.95   $207.00  
  7 purchase totals = $953.58       $1,028.9610   $1,028.96   $1,028.95   $1,029.00