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 $248.71   5.386%   $262.1055   $262.11   $262.10   $262.10  
  Purchase #2 $42.68   13.801%   $48.5703   $48.57   $48.55   $48.60  
  Purchase #3 $176.36   10.485%   $194.8513   $194.85   $194.85   $194.90  
  Purchase #4 $126.42   11.600%   $141.0847   $141.08   $141.10   $141.10  
  Purchase #5 $208.91   13.200%   $236.4861   $236.49   $236.50   $236.50  
  Purchase #6 $185.41   11.511%   $206.7525   $206.75   $206.75   $206.80  
  Purchase #7 $73.69   13.850%   $83.8961   $83.90   $83.90   $83.90  
  7 purchase totals = $1,062.18       $1,173.7465   $1,173.75   $1,173.75   $1,173.90