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 $85.60   12.130%   $95.9833   $95.98   $96.00   $96.00  
  Purchase #2 $168.81   8.423%   $183.0289   $183.03   $183.05   $183.00  
  Purchase #3 $49.69   12.117%   $55.7109   $55.71   $55.70   $55.70  
  Purchase #4 $233.67   7.336%   $250.812   $250.81   $250.80   $250.80  
  Purchase #5 $194.33   4.538%   $203.1487   $203.15   $203.15   $203.10  
  Purchase #6 $239.56   9.716%   $262.8356   $262.84   $262.85   $262.80  
  Purchase #7 $69.74   13.164%   $78.9206   $78.92   $78.90   $78.90  
  7 purchase totals = $1,041.40       $1,130.4400   $1,130.44   $1,130.45   $1,130.30