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 $191.60   8.826%   $208.5106   $208.51   $208.50   $208.50  
  Purchase #2 $201.77   6.116%   $214.1103   $214.11   $214.10   $214.10  
  Purchase #3 $45.25   7.641%   $48.7076   $48.71   $48.70   $48.70  
  Purchase #4 $61.25   9.434%   $67.0283   $67.03   $67.05   $67.00  
  Purchase #5 $230.68   9.244%   $252.0041   $252.00   $252.00   $252.00  
  Purchase #6 $148.31   3.863%   $154.0392   $154.04   $154.05   $154.00  
  Purchase #7 $175.83   3.294%   $181.6218   $181.62   $181.60   $181.60  
  7 purchase totals = $1,054.69       $1,126.0219   $1,126.02   $1,126.00   $1,125.90