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 $62.32   10.129%   $68.6324   $68.63   $68.65   $68.60  
  Purchase #2 $214.46   11.532%   $239.1915   $239.19   $239.20   $239.20  
  Purchase #3 $11.44   5.529%   $12.0725   $12.07   $12.05   $12.10  
  Purchase #4 $64.86   4.872%   $68.02   $68.02   $68.00   $68.00  
  Purchase #5 $226.50   9.459%   $247.9246   $247.92   $247.90   $247.90  
  Purchase #6 $124.37   7.726%   $133.9788   $133.98   $134.00   $134.00  
  Purchase #7 $213.91   13.212%   $242.1718   $242.17   $242.15   $242.20  
  7 purchase totals = $917.86       $1,011.9916   $1,011.98   $1,011.95   $1,012.00