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 $95.63   11.863%   $106.9746   $106.97   $106.95   $107.00  
  Purchase #2 $158.97   9.852%   $174.6317   $174.63   $174.65   $174.60  
  Purchase #3 $158.86   10.585%   $175.6753   $175.68   $175.70   $175.70  
  Purchase #4 $67.87   8.333%   $73.5256   $73.53   $73.55   $73.50  
  Purchase #5 $203.78   4.843%   $213.6491   $213.65   $213.65   $213.60  
  Purchase #6 $207.25   5.377%   $218.3938   $218.39   $218.40   $218.40  
  Purchase #7 $82.78   4.869%   $86.8106   $86.81   $86.80   $86.80  
  7 purchase totals = $975.14       $1,049.6607   $1,049.66   $1,049.70   $1,049.60