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 $241.66   8.425%   $262.0199   $262.02   $262.00   $262.00  
  Purchase #2 $84.89   9.497%   $92.952   $92.95   $92.95   $93.00  
  Purchase #3 $238.90   11.565%   $266.5288   $266.53   $266.55   $266.50  
  Purchase #4 $227.92   4.642%   $238.5   $238.50   $238.50   $238.50  
  Purchase #5 $47.39   9.757%   $52.0138   $52.01   $52.00   $52.00  
  Purchase #6 $182.57   4.769%   $191.2768   $191.28   $191.30   $191.30  
  Purchase #7 $221.42   9.414%   $242.2645   $242.26   $242.25   $242.30  
  7 purchase totals = $1,244.75       $1,345.5558   $1,345.55   $1,345.55   $1,345.60