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 $114.60   9.111%   $125.0412   $125.04   $125.05   $125.00  
  Purchase #2 $186.73   10.160%   $205.7018   $205.70   $205.70   $205.70  
  Purchase #3 $88.57   4.259%   $92.3422   $92.34   $92.35   $92.30  
  Purchase #4 $244.69   8.586%   $265.6991   $265.70   $265.70   $265.70  
  Purchase #5 $243.65   3.531%   $252.2533   $252.25   $252.25   $252.30  
  Purchase #6 $235.33   12.639%   $265.0734   $265.07   $265.05   $265.10  
  Purchase #7 $130.50   13.783%   $148.4868   $148.49   $148.50   $148.50  
  7 purchase totals = $1,244.07       $1,354.5978   $1,354.59   $1,354.60   $1,354.60