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 $88.61   8.342%   $96.0018   $96.00   $96.00   $96.00  
  Purchase #2 $153.57   5.133%   $161.4527   $161.45   $161.45   $161.50  
  Purchase #3 $214.71   7.396%   $230.59   $230.59   $230.60   $230.60  
  Purchase #4 $102.47   6.823%   $109.4615   $109.46   $109.45   $109.50  
  Purchase #5 $136.94   7.361%   $147.0202   $147.02   $147.00   $147.00  
  Purchase #6 $109.94   7.215%   $117.8722   $117.87   $117.85   $117.90  
  Purchase #7 $185.47   9.615%   $203.3029   $203.30   $203.30   $203.30  
  7 purchase totals = $991.71       $1,065.7013   $1,065.69   $1,065.65   $1,065.80