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 $94.73   3.715%   $98.2492   $98.25   $98.25   $98.20  
  Purchase #2 $120.64   6.144%   $128.0521   $128.05   $128.05   $128.10  
  Purchase #3 $186.40   5.438%   $196.5364   $196.54   $196.55   $196.50  
  Purchase #4 $156.87   10.637%   $173.5563   $173.56   $173.55   $173.60  
  Purchase #5 $185.78   11.862%   $207.8172   $207.82   $207.80   $207.80  
  Purchase #6 $178.36   4.440%   $186.2792   $186.28   $186.30   $186.30  
  Purchase #7 $210.93   3.496%   $218.3041   $218.30   $218.30   $218.30  
  7 purchase totals = $1,133.71       $1,208.7945   $1,208.80   $1,208.80   $1,208.80