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 $228.72   7.246%   $245.2931   $245.29   $245.30   $245.30  
  Purchase #2 $237.37   10.231%   $261.6553   $261.66   $261.65   $261.70  
  Purchase #3 $14.91   12.856%   $16.8268   $16.83   $16.85   $16.80  
  Purchase #4 $42.39   13.400%   $48.0703   $48.07   $48.05   $48.10  
  Purchase #5 $149.76   10.831%   $165.9805   $165.98   $166.00   $166.00  
  Purchase #6 $247.37   4.718%   $259.0409   $259.04   $259.05   $259.00  
  Purchase #7 $241.75   9.104%   $263.7589   $263.76   $263.75   $263.80  
  7 purchase totals = $1,162.27       $1,260.6258   $1,260.63   $1,260.65   $1,260.70