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 $236.33   11.137%   $262.6501   $262.65   $262.65   $262.70  
  Purchase #2 $183.40   10.212%   $202.1288   $202.13   $202.15   $202.10  
  Purchase #3 $216.49   9.337%   $236.7037   $236.70   $236.70   $236.70  
  Purchase #4 $204.30   13.657%   $232.2013   $232.20   $232.20   $232.20  
  Purchase #5 $230.77   10.556%   $255.1301   $255.13   $255.15   $255.10  
  Purchase #6 $215.74   9.852%   $236.9947   $236.99   $237.00   $237.00  
  Purchase #7 $182.28   13.491%   $206.8714   $206.87   $206.85   $206.90  
  7 purchase totals = $1,469.31       $1,632.6801   $1,632.67   $1,632.70   $1,632.70