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 $241.87   8.563%   $262.5813   $262.58   $262.60   $262.60  
  Purchase #2 $27.53   7.793%   $29.6754   $29.68   $29.70   $29.70  
  Purchase #3 $227.54   7.441%   $244.4713   $244.47   $244.45   $244.50  
  Purchase #4 $224.86   5.639%   $237.5399   $237.54   $237.55   $237.50  
  Purchase #5 $153.72   6.850%   $164.2498   $164.25   $164.25   $164.20  
  Purchase #6 $237.95   6.450%   $253.2978   $253.30   $253.30   $253.30  
  Purchase #7 $5.91   13.291%   $6.6955   $6.70   $6.70   $6.70  
  7 purchase totals = $1,119.38       $1,198.5110   $1,198.52   $1,198.55   $1,198.50