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 $69.67   9.411%   $76.2266   $76.23   $76.25   $76.20  
  Purchase #2 $200.76   3.598%   $207.9833   $207.98   $208.00   $208.00  
  Purchase #3 $119.58   9.744%   $131.2319   $131.23   $131.25   $131.20  
  Purchase #4 $242.37   7.261%   $259.9685   $259.97   $259.95   $260.00  
  Purchase #5 $46.62   9.517%   $51.0568   $51.06   $51.05   $51.10  
  Purchase #6 $225.71   11.634%   $251.9691   $251.97   $251.95   $252.00  
  Purchase #7 $169.60   3.375%   $175.324   $175.32   $175.30   $175.30  
  7 purchase totals = $1,074.31       $1,153.7602   $1,153.76   $1,153.75   $1,153.80