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 $168.61   8.559%   $183.0413   $183.04   $183.05   $183.00  
  Purchase #2 $229.95   10.256%   $253.5337   $253.53   $253.55   $253.50  
  Purchase #3 $238.93   3.157%   $246.473   $246.47   $246.45   $246.50  
  Purchase #4 $15.68   5.424%   $16.5305   $16.53   $16.55   $16.50  
  Purchase #5 $155.90   4.807%   $163.3941   $163.39   $163.40   $163.40  
  Purchase #6 $187.71   10.679%   $207.7556   $207.76   $207.75   $207.80  
  Purchase #7 $56.70   10.477%   $62.6405   $62.64   $62.65   $62.60  
  7 purchase totals = $1,053.48       $1,133.3687   $1,133.36   $1,133.40   $1,133.30