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 $69.58   4.555%   $72.7494   $72.75   $72.75   $72.70  
  Purchase #2 $228.37   5.176%   $240.1904   $240.19   $240.20   $240.20  
  Purchase #3 $159.61   10.441%   $176.2749   $176.27   $176.25   $176.30  
  Purchase #4 $179.63   4.474%   $187.6666   $187.67   $187.65   $187.70  
  Purchase #5 $165.47   6.326%   $175.9376   $175.94   $175.95   $175.90  
  Purchase #6 $98.78   8.600%   $107.2751   $107.28   $107.30   $107.30  
  Purchase #7 $67.83   6.253%   $72.0714   $72.07   $72.05   $72.10  
  7 purchase totals = $969.27       $1,032.1654   $1,032.17   $1,032.15   $1,032.20