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 $46.98   10.596%   $51.958   $51.96   $51.95   $52.00  
  Purchase #2 $160.63   13.684%   $182.6106   $182.61   $182.60   $182.60  
  Purchase #3 $12.31   7.629%   $13.2491   $13.25   $13.25   $13.20  
  Purchase #4 $230.58   8.261%   $249.6282   $249.63   $249.65   $249.60  
  Purchase #5 $242.39   8.861%   $263.8682   $263.87   $263.85   $263.90  
  Purchase #6 $169.72   3.471%   $175.611   $175.61   $175.60   $175.60  
  Purchase #7 $125.34   3.866%   $130.1856   $130.19   $130.20   $130.20  
  7 purchase totals = $987.95       $1,067.1107   $1,067.12   $1,067.10   $1,067.10